Four Japanese soldiers were injured Monday following an explosion at a storage facility for unexploded ordnance located within a United States military base on Okinawa, local and defence officials confirmed, as reported by AP.

The injuries are not considered life-threatening.

The incident occurred at a facility managed by the Okinawa prefectural government, located within the munitions storage area of Kadena Air Base.

According to the US Air Force, no American personnel were involved.

The explosion took place while the soldiers, part of Japan’s Self Defense Forces, were inspecting an unexploded device.

Japan’s public broadcaster NHK reported the blast occurred during an attempt to remove rust from the device. The cause of the explosion remains under investigation.

The facility temporarily stores wartime ordnance, most of it remnants from World War II.

Okinawa was the site of one of the war’s fiercest battles, and unexploded bombs are still frequently uncovered during construction and land development. It is estimated that more than 1,800 tons of unexploded US bombs remain buried across the island.

Monday’s accident marked the first such incident involving Japan’s ordnance disposal unit since it was established in 1974.

In a separate incident last October, a US wartime bomb detonated at a commercial airport in southern Japan, creating a large crater and disrupting air traffic. (PUNCH)

• Photo caption: U.S military persons gather near the site of an explosion at a storage site for unexploded ordnances at a U.S military base, Okinawa, Southern Japan, on Monday…Photo Credit: Kyodo News via AP