Multiple explosions and a large fire at a US Army depot lit up the night sky in a Tokyo suburb, but no injuries were reported.
The blast happened after midnight at the Sagami General Depot in Sagamihara, a city about 25 miles south-west of Tokyo.
The building that exploded was storing compressed nitrogen, oxygen, Freon and air, a statement issued by the US Army Japan said.
Photos taken after daybreak and released by the Army show dozens of grey canisters lying on the floor, and what looks like mangled storage racks.
The walls of the one-storey, concrete building remain intact, but the windows and doors are damaged and about half of the roof collapsed, the Army said. There are no indications of injuries.
Video on Japanese television, apparently shot from an elevated place outside the post, shows a fire in the distance and subsequent explosions shooting small fiery blasts into the sky. A woman told national broadcaster NHK that it sounded like fireworks.
About 500 Japanese and 300 American troops and civilians work at the depot, said Lieutenant Colonel Kevin Toner, the chief of public affairs for US Army Japan.
The sprawling 484-acre depot is in the middle of a heavily populated area, and at least one resident reported smoke coming into his home.
The US has about 50,000 troops stationed in Japan.
“This sort of incident triggers anxiety among residents living near the US bases, and we urge the US to provide further information, to investigate the cause and to prevent the repetition of such incidents,” Japanese government spokesman Yoshihide Suga said.
Base firefighters were joined by Japanese emergency responders in fighting the fire to prevent its spread to nearby buildings, the Army said.
The cause of the explosion is under investigation.