The Pentagon said that a US Army base in Japan was hit by an explosion and fire was triggered.
However, no injuries were reported in the Sunday's blast, Xinhua reported.
The explosion happened just after midnight local time at a building at the Sagami Depot, a US Army post in Sagamihara, said a Pentagon statement.
"There are no reports of injury, and base firefighters and first responders are currently fighting the resulting fire to prevent its spread to nearby buildings," said the statement.
US daily The Wall Street Journal reported that a spokesman for police in Kanagawa Prefecture, Japan, said two steel pipes were found planted in the ground with electric cables in the camp.