A fireworker investigates through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Firemen work through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Toru Hanai (JAPAN) 

Police officers hold cordon tapes near an annex to a spa's main building which it exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Firemen work through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Toru Hanai (JAPAN) 

A fireman looks through rubble after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Fireworkers and police officers investigate at an annex to a spa's main building where it exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

A fireworker searches through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Rescue workers are packed near an annex to a spa's main building where it exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Firemen and police officers work through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Toru Hanai (JAPAN) 

Firemen work through rubbles after an annex to a spa's main building exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN) 

Police officers shout near an annex to a spa's main building where it exploded in Tokyo June 19, 2007. An explosion ripped through the women's-only hot spring spa in downtown Tokyo on Tuesday, injuring several people, at least one seriously, media and police said. REUTERS/Yuriko Nakao (JAPAN)