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

The United States Coast Guard said on Monday night it had located the bodies of 25 people, after a dive boat anchored off the coast of Southern California caught fire and sank.

Nine people remain unaccounted for.

Lt. Cmdr. Matthew Kroll of the US Coast Guard said the authorities had recovered 20 bodies and identified the location of five more.

Those five cannot be recovered due to unsafe conditions under the ship, which had been on a three-day scuba diving excursion to the Channel Islands, northwest of Los Angeles.

Kroll said the bodies that had been recovered 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.

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.

BREAKING NEWS: The Coast Guard has launched multiple rescue assets along with assets from local agencies to assist more than 30 people in distress on a 75ft boat near Santa Cruz Island. More details will be available later as this operation continues. — USCG Los Angeles (@USCGLosAngeles) September 2, 2019

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 on Saturday morning with plans to return on 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.