TEHRAN – A ship at the U.S. Naval base in San Diego has caught fire which according to reports, has injured at least 21 people on board.

USS Bonhomme Richard belongs to the Essex-class aircraft carriers and earned one battle star during the Second World War. According to Krishna Jackson of Naval Base San Diego, prior to the incident, the USS Bonhomme Richard underwent a regular maintenance cycle, Sputnik reported.

Firefighters battled a blaze on board the USS Bonhomme Richard at a naval base in San Diego on Sunday, local media reported. The ship caught fire early on Sunday and an explosion occurred on board.

At least 21 people, including four civilians, were injured amid the fire, the Naval Surface Forces of the U.S. Pacific Fleet said.

According to images circulating online, several fireboats were deployed to extinguish the flames, which was concentrated in the center portion of the vessel. An explosion was also heard on board the ship prior to the blaze, according to domestic media reports.

The cause of the blaze was not immediately clear, while the San Diego Police Department has not responded for a comment. There were, meanwhile, indications that the ship could continue burning for days.

All crew members have safely evacuated the vessel and all are accounted for, the naval fleet said in an earlier Tweet.

The USS Bonhomme Richard was commissioned in 1998 and spent six years in Japan as part of the US Navy’s Forward Deployed Naval Force in the region.