Image copyright Ventura County Fire Department Image caption A fire department photo showing the burned out boat

Twenty-five bodies have been found after a boat was destroyed by fire off the coast of California, officials say.

Citing the US Coast Guard, media reports said nine people were missing, while five crew members had survived.

The fire started in the early hours of Monday, while the boat was anchored metres off Santa Cruz Island, about 90 miles (145km) west of Los Angeles.

Search teams worked throughout Monday night. The cause of the blaze was not immediately clear.

At a news conference, Sheriff Bill Brown confirmed 39 people were on board the vessel when fire broke out.

The Conception - a 75-foot-long (23m) commercial diving boat - is now completely submerged.

What happened on the ship?

Coast Guard services overheard a mayday call at 03:30 local time (10:30 GMT) on Monday, saying that the boat was engulfed in flames. Those killed are thought to have been trapped below deck.

Media playback is unsupported on your device Media caption California residents mourn victims of a boat disaster

The Associated Press news agency and CBS news cited Coast Guard officials as saying 25 people are confirmed dead.

Those who escaped the fire may have been sleeping in the main cabin of the boat rather than below. They were awake and had jumped off the boat's bridge, making their way to another vessel called the Grape Escape.

The Grape Escape was moored a few hundred feet away, according to the New York Times.

The owner of the Grape Escape, Bob Hansen, told the Times he and his wife were woken up by the crewmen - soaked and shivering - frantically knocking on their vessel.

Mr Hansen said when he stepped out of his cabin, he could see the Conception was engulfed in flames, "from stem to stern".

"I could see the fire coming through holes on the side of the boat," he said. "There were these explosions every few beats. You can't prepare yourself for that. It was horrendous."

Image copyright EPA Image caption The boat was totally engulfed in flames as crews tried to reach those onboard

Sheriff Brown said that oxygen or propane tanks could have exploded during the fire, but there was no sign this sparked the blaze.

"Nothing in the [mayday] broadcast from the vessel... indicated there was an initial explosion," he said.

In the mayday call, a man is heard frantically telling the operator "I can't breathe". He describes the boat ablaze with "no escape hatch for any of the people on board".

Capt Rochester said the boat was "fully in compliance" with safety regulations, and had no prior violations.

The owner of a Santa Cruz diving company, Kristy Finstad, was reportedly one of the Conception's passengers, according to CBS San Francisco.

Ms Finstad was named by her brother, who posted on Facebook: "Please pray for my sister Kristy!! She was leading a dive trip on this boat."

None of the victims have been named by officials.

Image copyright Getty Images Image caption A makeshift memorial has been set up on the docks where the Conception was based

Sheriff Brown said the fire was "probably the worst case scenario you could possibly have" on a vessel, as it was in open water at night with most people asleep below decks.

"Fire is the scourge of any ship," he said. "Of all scenarios... you couldn't ask for a worse situation."

The Conception sank 20 yards (18m) off the north shore of Santa Cruz Island, at the depth of 64ft (20m).

Run by a diving company called Truth Aquatics, which has a 4.5 rating on Trip Advisor, Conception was used for chartered trips in the Channel Islands National Park. It was on the final day of a three day scuba diving excursion for the Labor Day weekend.

The boat's layout shows three rows of double bunks with a shower room at the front of the boat. "Pillows, blankets, reading lights, privacy curtain and personal storage are provided," the company's website said.