An unexploded U.S. bomb from World War II that had been buried at a Japanese airport exploded Wednesday, causing a large crater in a taxiway and the cancellation of more than 80 flights but no injuries, Japanese officials said.

Land and Transport Ministry officials said there were no aircraft nearby when the bomb exploded at Miyazaki Airport in southwestern Japan.

Officials said an investigation by the Self-Defense Forces and police confirmed that the explosion was caused by a 500-pound U.S. bomb and there was no further danger. They were determining what caused its sudden detonation.