An explosion rocked a warehouse at a U.S. military base in Sagamihara, Kanagawa Prefecture, about 40 km southwest of Tokyo, but there were no reports of injuries, fire officials said on Monday.
The local fire department said it received a call just after midnight of an explosion at the warehouse, where it said "dangerous material" is stored.
It dispatched firefighters, and said later the blaze had subsided with little danger of it spreading since there were no adjacent buildings. The cause of the fire was not immediately known but metal oxygen tanks in the warehouse may have exploded, firefighters said.