A crew member works to clear debris the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICO - Tags: DISASTER HEALTH) 

Crew members work to clear debris the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City, January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICO - Tags: DISASTER HEALTH) 

Police officers put on face masks as they stand guard the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City, January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICODISASTER - Tags: DISASTER HEALTH) 

Crew workers queuing up are reflected in broken glass, the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City, January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICO - Tags: DISASTER HEALTH TPX IMAGES OF THE DAY) 

A crew member works to clear debris the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City, January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICO - Tags: DISASTER HEALTH) 

Crew members work to clear debris the day after a deadly gas truck explosion ripped through a maternity hospital in Mexico City, January 30, 2015. The gas truck explosion ripped through the maternity hospital on the western edge of Mexico City on Thursday, killing one woman and two children and injuring dozens, authorities said, with several babies found alive in the rubble. Some of the injured were evacuated by helicopter, and aerial footage showed firefighters scrambling over the skeletal wreckage of the building. REUTERS/Edgard Garrido (MEXICO - Tags: DISASTER HEALTH) 

Supporters accompany a fire truck carrying the coffin of the late Brazilian presidential candidate Eduardo Campos towards a cemetery for burial in Recife, August 17, 2014. Tens of thousands of Brazilians gathered on Sunday in the northeastern city of Recife to bid farewell to presidential candidate Campos, killed in a plane crash four days ago, as debate swirled about the impact of his death on the October election. REUTERS/Paulo Whitaker (BRAZIL - Tags: DISASTER POLITICS OBITUARY ELECTIONS TPX IMAGES OF THE DAY) 

Residents watch firefighters battle the so-called Poinsettia Fire in Carlsbad, California May 14, 2014. At least two structures burned to the ground and some 15,000 homes and businesses were told to evacuate on Wednesday as the wind-lashed wildfire roared out of control in the heart of a Southern California coastal community. The blaze, which erupted shortly before 11 a.m. in Carlsbad, some 25 miles north of San Diego, quickly became the most pressing battle for crews fighting flames across the region amid soaring temperatures and hot Santa Ana winds. REUTERS/Sam Hodgson (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

A helicopter drops water on a burning hillside next to homes as firefighters battle the Bernardo Fire, north of San Diego, California May 13, 2014. More than 20,000 homes and other residences were being evacuated in and around San Diego on Tuesday as a fast-moving California wildfire driven by high winds blackened more than a square mile, fire and county officials said. REUTERS/Mike Blake (UNITED STATES - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY) 

Austrian firefighters stand in an aerial lift in front of a partially collapsed house in Vienna April 26, 2014. The house collapsed after an explosion and five residents were seriousely injured according to police. The cause of the explosion was unclear, according to the authorities. REUTERS/Leonhard Foeger (AUSTRIA - Tags: DISASTER) 

Austrian firefighters stand in an aerial lift in front of a partially collapsed house in Vienna April 26, 2014. The house collapsed after an explosion and five residents were seriousely injured according to police. The cause of the explosion was unclear, according to the authorities. REUTERS/Leonhard Foeger (AUSTRIA - Tags: DISASTER) 

An aerial view of the wreckage of a slum is seen after a fire broke out, at Modhubagh in Dhaka February 8, 2014. A child was burnt alive and hundreds of shanties were gutted during the fire that originated from a cooking oven at a slum in the Modhubagh area of Dhaka on Saturday, firefighters said. REUTERS/Andrew Biraj (BANGLADESH - Tags: DISASTER) 

An aerial view of the wreckage of a slum is seen after a fire broke out, at Modhubagh in Dhaka February 8, 2014. A child was burnt alive and hundreds of shanties were gutted during the fire that originated from a cooking oven at a slum in the Modhubagh area of Dhaka on Saturday, firefighters said. REUTERS/Andrew Biraj (BANGLADESH - Tags: DISASTER) 

A "super scooper" air tanker makes waters drops as firefighters battle a fast-moving California wildfire, so-called the "Colby Fire", in the hills of Glendora January 16, 2014. The wildfire, started accidentally by three campers, roared out of control in foothills above Los Angeles on Thursday, destroying at least two homes and forcing more than 1,000 residents to flee, fire and law enforcement officials said. The wind-whipped blaze erupted before dawn in the Angeles National Forest north of Glendora, about 40 miles east of downtown Los Angeles in the foothills of the San Gabriel Mountains. REUTERS/Gene Blevins (UNITED STATES - Tags: DISASTER ENVIRONMENT TRANSPORT) 

A helicopter assists in fighting a forest fire in the rural town of Melipilla of the Bollenar area, about 71 km (44 miles) southwest of Santiago, January 7, 2014. According to local authorities, more than 17,000 hectares of land in central and southern Chile have been burned due to multiple fires, with no deaths or injuries reported currently. Picture taken January 7, 2014. REUTERS/Ivan Alvarado (CHILE - Tags: TRANSPORT DISASTER ENVIRONMENT SOCIETY) 

Aerial view shows a burned out area along Pfeiffer Ridge in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows a burned out area along Pfeiffer Ridge in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows a burned out area along Pfeiffer Ridge in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows a burned out area along Pfeiffer Ridge in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows smoke rising from a wildfire in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows a burned out area along Pfeiffer Ridge in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

Aerial view shows smoke rising from a wildfire in Big Sur, California, December 19, 2013. Firefighters battling the Pfeiffer Fire that has destroyed 22 homes along California's scenic Big Sur coastline were counting on lower temperatures and more favorable wind conditions to help them suppress the flames. REUTERS/Michael Fiala (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

A helicopter drops water on a fire approaching homes near the Blue Mountains suburb of Blackheath, located around 70 km (43 miles) west of Sydney, October 23, 2013. A state of emergency has been declared in the Australian state of New South Wales, as bushfires continue to burn west of Sydney and weather conditions expected to worsen over the coming days. Around 60 fires are still burning across the state. REUTERS/David Gray (AUSTRALIA - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

Smoke rises from the aftermath of a boardwalk fire in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

Smoke rises from the aftermath of a boardwalk fire in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

The aftermath of a boardwalk fire is seen in this aerial photograph over Seaside Park, New Jersey, September 13, 2013. New Jersey Governor Chris Christie vowed on Friday to rebuild two resort towns ravaged by a boardwalk fire just months after they were restored in the aftermath of Superstorm Sandy, while state officials put out a call for federal aid. About 100 firefighters remained on the scene on Friday, putting out hot spots after containing the fire which started at a frozen custard stand in Seaside Park on Thursday and blazed out of control for hours, moving several blocks into neighboring Seaside Heights. REUTERS/Adrees Latif (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

A helicopter drops water on the Morgan fire as it advances down a rugged hillside at Mount Diablo State Park near Clayton, California September 9, 2013. The small, but fast-growing brush fire threatens about 50 to 75 homes according to a California Department of Forestry and Fire Protection spokeswoman. REUTERS/Noah Berger (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

A helicopter drops water over a forest fire in Adsamu village, near Vouzela August 23, 2013. One firefighter died and six were injured yesterday, as they battled against a fire in Tondela region, according Portuguese authorities. REUTERS/Rafael Marchante (PORTUGAL - Tags: ENVIRONMENT DISASTER TPX IMAGES OF THE DAY TRANSPORT) 

A helicopter tanker drops fire retardant near a home at the Beaver Creek wildfire outside Ketchum, Idaho August 18, 2013. Firefighters readied for a massive ground and air attack on Sunday against a wildfire in central Idaho that has forced the evacuation of some 2,250 homes and threatens the posh Sun Valley ski resort. REUTERS/Jim Urquhart (UNITED STATES - Tags: DISASTER TPX IMAGES OF THE DAY) 

A helicopter air tanker dumps water as the sun sets at the Beaver Creek wildfire outside Hailey, Idaho August 17, 2013. A fast-moving central Idaho wildfire forced the evacuation of 2,250 homes near the tourist towns of Hailey and Ketchum as firefighters lost ground on Saturday against the blaze that also threatens the Sun Valley ski resort. REUTERS/Jim Urquhart (UNITED STATES - Tags: DISASTER TPX IMAGES OF THE DAY) 

A helicopter collects water from a pond near a home in the evacuated Golden Eagle subdivision during the Beaver Creek wildfire outside Hailey, Idaho August 16, 2013. Firefighters battled on Friday to check the fast-moving wildfire raging near the Sun Valley ski resort in Idaho, where more than 1,000 people were evacuated as flames menaced multimillion-dollar homes in the area, authorities said. REUTERS/Jim Urquhart (UNITED STATES - Tags: DISASTER ENVIRONMENT TRANSPORT) 

A helicopter fills a bucket of water for use in fighting the Rockport Fire near Rockport State Park in Utah August 14, 2013. The cause of the blaze in the scrub oak and sagebrush foothills about 40 miles (64 km) east of Salt Lake City was unknown but there were reports of lightning strikes in the area mid-afternoon when the blaze erupted, according to local media. REUTERS/Jim Urquhart REUTERS/Jim Urquhart (UNITED STATES - Tags: DISASTER TRANSPORT) 

An aerial view shows the Silver Fire raging on near Banning, California August 7, 2013. The wildfire raged out of control in the high desert east of Los Angeles on Wednesday, injuring two firefighters and one civilian and forcing the evacuation of hundreds of residents of three small communities. REUTERS/Gene Blevins (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view shows the Silver Fire raging on near Banning, California August 7, 2013. The wildfire raged out of control in the high desert east of Los Angeles on Wednesday, injuring two firefighters and one civilian and forcing the evacuation of hundreds of residents of three small communities. REUTERS/Gene Blevins (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

A firefighting aircraft drops water over a forest fire in Marathon near Athens August 5, 2013. A wildfire fanned by strong winds raged near Athens on Monday, damaging homes and sending residents fleeing, fire brigade officials said. Reuters witnesses said the blaze had damaged at least three homes at a hamlet by the town of Marathon - the site of the historic 490 BC battle between Athenians and Persians about 40 kilometres (25 miles) northeast of the Greek capital. REUTERS/Yannis Behrakis (GREECE - Tags: DISASTER ENVIRONMENT) 

Greek firefighters prepare to move as a firefighting aircraft flies overhead as a forest fire rages in Marathon near Athens August 5, 2013. A wildfire fanned by strong winds raged near Athens on Monday, damaging homes and sending residents fleeing, fire brigade officials said. Reuters witnesses said the blaze had damaged at least three homes at a hamlet by the town of Marathon - the site of the historic 490 BC battle between Athenians and Persians about 40 kilometres (25 miles) northeast of the Greek capital. REUTERS/Yannis Behrakis (GREECE - Tags: DISASTER ENVIRONMENT) 

A firefighting airplane drops water over a forest fire at Markopoulo region a few miles southwest of Athens August 2, 2013. REUTERS/Yorgos Karahalis (GREECE - Tags: DISASTER ENVIRONMENT) 

A firefighter stands close to the remains of a train wreckage in Lac Megantic July 8, 2013. A driverless, runaway fuel train that exploded in a deadly ball of flames in the center of a small Quebec town started rumbling down an empty track just minutes after a fire crew had extinguished a blaze in one of its parked locomotives, an eyewitness said on Monday. REUTERS/Mathieu Belanger (CANADA - Tags: DISASTER TRANSPORT TPX IMAGES OF THE DAY) 

Trees burned by the Yarnell Hill Fire stand along a hill side in Yavapai County, Arizona July 3, 2013. Firefighters labored on Wednesday to extend their grip on a smoldering but still potentially lethal blaze in Arizona that killed 19 members of an elite "hotshots" crew in the deadliest U.S. wildfire tragedy in eight decades. REUTERS/Joshua Lott (UNITED STATES - Tags: ENVIRONMENT DISASTER) 

An aerial view of a strip of fire retardant is seen that kept a large part of Yarnell, Arizona (R) from being destroyed July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

An aerial view of a strip of fire retardant is seen (lower R) that kept a large part of Yarnell, Arizona (L) from being destroyed July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a strip of fire retardant near Yarnell, Arizona that kept a large part of Yarnell, Arizona (R) from being destroyed is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separating the burned area from the green area is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separating the burned area from the green area is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separating the burned area from the green area is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separating the burned area from the green area is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separating the burned area from the green area is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

An aerial view of a strip of fire retardant near Yarnell, Arizona separates the burned area from the green area on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

An aerial view of a section of the town of Yarnell, Arizona that is destroyed by a wildland fire which ripped through the town is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a section of the town of Yarnell, Arizona that is destroyed by a wildfire which ripped through the town is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT TPX IMAGES OF THE DAY) 

An aerial view of a section of the town of Yarnell, Arizona that is destroyed by a wildfire which ripped through the town is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a section of the town of Yarnell, Arizona that is destroyed by a wildfire which ripped through the town is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT) 

An aerial view of a section of the town of Yarnell, Arizona that is destroyed by a wildfire which ripped through the town is seen on July 1, 2013. An elite squad of 19 Arizona firemen was killed in the worst U.S. wildland firefighting tragedy in 80 years apparently outflanked and engulfed by wind-whipped flames in seconds, before some could scramble into cocoon-like personal shelters. REUTERS/Rick Wilking (UNITED STATES - Tags: DISASTER ENVIRONMENT)