Eighteen people suffered minor injuries in an explosion and fire Sunday on board a ship at Naval Base San Diego, military officials said.

The blaze was reported shortly before 9 a.m. on USS Bonhomme Richard, said Mike Raney, a spokesman for Naval Surface Force, US Pacific Fleet.

Eighteen people were hospitalized with “non-life threatening injuries,” Raney said in a brief statement. He didn't have additional details.

Smoke rises from the USS Bonhomme Richard at Naval Base San Diego Sunday, July 12, 2020, in San Diego after an explosion and fire Sunday on board the ship at Naval Base San Diego. (AP PhotoDenis Poroy)

Smoke rises from the USS Bonhomme Richard at Naval Base San Diego Sunday, July 12, 2020, in San Diego after an explosion and fire Sunday on board the ship at Naval Base San Diego. (AP PhotoDenis Poroy)

Previously officials said at least one person was treated for smoke inhalation.

The cause of the fire was under investigation. It wasn't immediately known where on the 840-foot (255-meter) amphibious assault vessel the blast and the fire occurred.

The flames sent up a huge plume of dark smoke visible around San Diego.

Smoke rises from the USS Bonhomme Richard at Naval Base San Diego Sunday, July 12, 2020, in San Diego after an explosion and fire Sunday on board the ship at Naval Base San Diego. (AP PhotoDenis Poroy)

Smoke rises from the USS Bonhomme Richard at Naval Base San Diego Sunday, July 12, 2020, in San Diego after an explosion and fire Sunday on board the ship at Naval Base San Diego. (AP PhotoDenis Poroy)

San Diego is the Bonhomme Richard's home port and it was undergoing routine maintenance at the time of the fire.

About 160 sailors and officers were on board, Raney said — far fewer than the thousand typically on the ship when it's on active duty.

The ship has the capacity to deploy and land helicopters, smaller boats and amphibious vehicles.