Twenty-five bodies have been located and and nine people are still missing following a boat fire near southern California’s Santa Cruz Island, according to the Coast Guard.

In all, 39 passengers were aboard the “Conception,” a commercial diving boat based out of the Santa Barbara harbour, when it caught fire off the coast of Ventura County.

Only five people have escaped with the aid of a good Samaritan pleasure craft called “Great Escape.”

The five people rescued were the boat’s crew members who were in the main cabin at the time of the fire. Two suffered leg injuries, according to the LA Times. One crew member was still missing.

The US Coast Guard heard the boat’s mayday call around 3.15am. Fire department crews then began fighting the fire until the boat sank 20 metres off shore in 20 metres of water.

The Coast Guard says 25 people who died have been located and nine remain unaccounted for following a boat fire off the Southern California coast. https://t.co/4JHDQc4ysK

— The Associated Press (@AP) September 3, 2019

The Coast Guard searched the coastline of Santa Cruz Island for any other possible survivors but found none, officials said.

“This isn’t a day that we wanted to wake up to for Labor Day and it’s a very tragic event,” Coast Guard Captain Monica Rochester said.

“We will search all the way through the night into the morning but I think we all should be prepared to move into the worst outcome.”

Initially, four bodies were recovered from the area and divers found another four on the ocean floor near the sunken vessel, which was upside down in more than 18 metres of water, Santa Barbara County Sheriff Bill Brown said.

“Fire is the scourge of any ship,” Sheriff Brown said, and to be in a remote location, asleep and then have a fire spread quickly, “you couldn’t ask for a worse situation”.

The recovered bodies would have to be identified through DNA samples, Sheriff Brown said.

The Conception, which launched in 1981, embarked for California’s Channel Islands on Saturday morning with 39 people on board.

UPDATE: This photo shows the burned out “Conception just before it sank off the Santa Cruz Island coast. Latest here: https://t.co/k37XtD6Lga (Courtesy: @VCFD_PIO) pic.twitter.com/LEaSkLHYBv

— CBS Los Angeles (@CBSLA) September 2, 2019

Authorities were trying to determine the best way to recover the sunken vessel, including the possibility of towing it to shore, Sheriff Brown said.

Surviving crew members sought refuge on a fishing boat moored nearby, banging on the side to wake up Bob Hansen and his wife, who were sleeping onboard.

“When we looked out, the other boat was totally engulfed in flames, from stem to stern,” Mr Hansen told The New York Times.

“There were these explosions every few beats. You can’t prepare yourself for that. It was horrendous.”

Hear the mayday call:

Scuba or propane tanks on the Conception might have exploded in the fire, but that had not been confirmed, Sheriff Brown said. He said it was unclear if there was an initial explosion that caused the fire.

After borrowing clothes from the Hansens, some crew members headed back toward the Conception to look for survivors without luck, Mr Hansen said.