Some 39 people were on board scuba diving boat that caught fire off and sank off coast of Southern California coast.

The United States Coast Guard said on Monday at least eight people had been confirmed dead after a dive boat anchored off the coast of Southern California caught fire and sank.

Rescuers recovered four bodies from the sea just off Santa Cruz Island – about 145 kilometres northwest of Los Angeles – and spotted four others near where the vessel went down.

qatar airways

The search for the 26 people who remained missing was continuing, but Coast Guard Capt. Monica Rochester cautioned that it was unlikely anyone else would be found alive.

“We should all be prepared to move into the worst outcome,” she told an afternoon news conference.

Matthew Kroll of the US Coast Guard said the bodies had injuries consistent with drowning.

Five crew members managed to escape when the fire broke out and were rescued by people on a boat nearby.

Authorities have given fluctuating information about the number of people on board the vessel. The Coast Guard said a sixth crew member named on the manifest was actually not on board.

California boat fire
In this photo released by the Ventura County Fire Department, firefighters attempt to extinguish a fire on a boat off the coast of Santa Cruz Island, California [Handout/Ventura County Fire Department/AFP]

The Los Angeles sector of the US Coast Guard said earlier that more than 30 people were “in distress” on board the boat.

“A group of crew members has been rescued [ones with minor injuries] and efforts continue to evacuate the remaining passengers,” the Coast Guard tweeted early on Monday.

“The vessel was reported as being on fire,” it said.

According to the Associated Press, the boat was on a Labor Day cruise, taking divers to the Channel Islands.

The vessel, Conception, was operated by Santa Barbara-based Worldwide Diving Adventures, which said on its website it has been operating such expeditions since 1972.

This weekend trip had departed early Saturday morning with plans to return early Monday evening.

The boat was outfitted with dozens of small berths for people to sleep in overnight.

It was not immediately clear when divers would be able to search the boat for the missing.

“It’s upside down in relatively shallow water with receding tides that are moving it around,” Santa Barbara County Sheriff Bill Brown said.