A dying bird covered in spilled oil lies on a rock on the banks of the San Juan river in Cadereyta, Mexico August 26, 2014. An oil pipeline spill that contaminated a river in the northern Mexican state of Nuevo Leon will take months to clean up, the country's top water authority said. The 24-inch Madero-Cadereyta pipeline, owned by national oil company Pemex, was ruptured when thieves attempted to tap into it, the company said. REUTERS/Daniel Becerril

Workers take a break while trying to clean the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

The reflection of a worker is seen in leaked oil as he tries to recover oil from the shores of the river San Juan in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A dead bird covered in spilled oil lies in the San Juan river in Cadereyta August 26, 2014. REUTERS/Daniel Becerril

Workers pour oil into containers while trying to clean the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

A bird covered in oil stretches its wings on the shores of the river San Juan in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A worker cuts reed while trying to clean the area from leaked oil at an irrigation canal that flows into the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

Workers try to clean up leaking oil at a stream in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

The reflection of a worker is seen in leaked oil on the shores of the river San Juan in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A bird covered in spilled oil perches on the banks of the San Juan river in Cadereyta August 26, 2014. REUTERS/Daniel Becerril

Oil-stained tail feathers of a dead bird are seen on the banks of San Juan river in Cadereyta August 26, 2014. REUTERS/Daniel Becerril

Workers navigate near containment booms while trying to clean the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

A worker uses a shovel to row through leaked oil on the San Juan river in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

Workers cut reed while trying to clean the area from leaked oil at an irrigation canal that flows into the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

The sun is reflected in leaked oil on the shores of an irrigation canal that flows into the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril

Cattle stand in a stream near leaked oil in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A part of the oil pipeline, where thieves had tried to tap into, is seen uncovered and surrounded by yellow tape in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

Workers try to clean up leaking oil at a stream in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A woman observes as workers try to clean leaking oil in the river San Juan in Cadereyta August 21, 2014. REUTERS/Daniel Becerril

A dead dragonfly, covered in oil, lies on the shore of an irrigation canal that flows into the river San Juan in Cadereyta August 22, 2014. REUTERS/Daniel Becerril