The explosions occurred at the Sagami General Depot in Sagamihara City, Japan, according to Shingetsu News Agency.
Those in Sagamihara City, where the depot for the US military houses ammunition, heard loud blasts around 1am local time on Monday morning.
Video of the incident showed repeated blasts of light coming from the base as smoke billowed into the air.
One resident told Japanese broadcaster NHK that she was awoken by what sounded like thunder before seeing the bright orange blaze.
She described smelling a gunpowder-like odor as the explosions continued for about 10 minutes.
Fire trucks have been called to the scene, which is 25 miles southwest of the Tokyo metro area in the Kaganawa Prefecture.
About 580 people work at the facility, according to NHK. Residents in the area have not been evacuated.
Shingetsu said that the initial explanation for the blasts was that there had been an 'accidental fire' at a storehouse holding explosives.
The US military also houses soldiers near Sagamihara at Camp Zama, mail online reported.
In April of this year three explosions were heard near the base, according to the Wall Street Journal. Police expected that the blasts were from left-wing Japanese extremists.
There were no immediate reports of injuries or death in Monday morning's explosions.
Pentagon spokesman US Navy Commander Bill Urban told Reuters, "We're aware of the report, but we don't have confirmation that the explosion occurred on the base."