WASHINGTON (AFP) – An explosion struck a U.S. naval weapons station in New Jersey on Tuesday, injuring eight people, including one seriously, officers said.

The explosion occurred in the morning “while personnel were doing routine maintenance on a utility boat,” said Navy spokesman Lieutenant Greg Raelson in a statement.

One person was being treated at a local hospital while seven others suffered minor injuries in the explosion at the Naval Weapons Station Earle in Middletown, New Jersey, he said.

Ammunition and ordnance operations at the facility were “not affected” by the blast.

About 1,500 people work at the naval station, which is used as a weapons depot and for ship repairs.

“The cause of the explosion is under investigation,” he said.