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.