At least 18 sailors were reported injured Sunday after an apparent explosion and fire on a military ship in San Diego, California.

Authorities were working to put out a fire on the USS Bonhomme Richard, according to the San Diego Fire-Rescue Department. The agency said federal firefighters had joined efforts to extinguish the blaze, the cause of which was not reported.

San Diego Fire-Rescue said it responded about 9 a.m. local time when second alarm was called for the fire. A third alarm was called at 9:51 a.m., the department tweeted.

All firefighters from the San Diego department were accounted for by 11:19 a.m., but it was unclear whether the fire had been extinguished.

Naval Base San Diego tweeted that at least 18 sailorswere taken to the hospital for non-life-threatening injuries, and that all the crew had been accounted for. Approximately 160 crew members were on board at the time of the fire.

Krishna Jackson, public affairs officer for Naval Base San Diego, told NBC San Diego that the ship had undergone a regular maintenance cycle before the fire was reported.

Naval Base San Diego did not immediately respond to a call for more information from NBC News Sunday.

The USS Bonhomme Richard is an amphibious assault ship, which works to deploy and land elements of a Marine landing force. San Diego became home to the ship in 2018, after six years docked in Japan, according to the U.S. Naval Institute.