Multiple explosions and a large fire damaged a U.S. Army depot in a suburb of Tokyo early Monday, but no injuries were reported.

The blast happened after midnight (11 a.m. Sunday EDT) at the Sagami General Depot in Sagamihara, a city about 25 miles southwest of Tokyo, said Navy Commander Bill Urban, a Pentagon press officer.

"There are no indications of injuries," Pentagon spokesman U.S. Navy Commander Bill Urban said in a statement. "The army appreciates the quick reaction and support of our partners from the Sagamihara City emergency services." Urban added that the cause of the explosion was still under investigation.

The building that exploded was storing compressed nitrogen, oxygen, Freon and air, a statement issued by the U.S. Army Japan said. Photos taken after daybreak and released by the Army show dozens of gray canisters lying on the floor, and what looks like mangled storage racks.

The walls of the one-story, concrete building remain intact, but the windows and doors are damaged and about half of the roof collapsed, the Army said.

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 Lt. Col. Kevin Toner, the chief of public affairs for U.S. 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 U.S. has about 50,000 troops stationed in Japan.

"This sort of incident triggers anxiety among residents living near the U.S. bases, and we urge the U.S. to provide further information, to investigate the cause and to prevent the repetition of such incidents," Yoshihide Suga, the government's top spokesman, said at his morning briefing.

Base firefighters were joined by Japanese emergency responders in fighting the fire to prevent its spread to nearby buildings, the Army said.

Three explosions linked to a left-wing extremist group were reported in the vicinity of the base in April, according to the Wall Street Journal.

The Associated Press contributed to this report.