Emergency services have found 25 bodies off the Californian coast following a fire on a dive boat.

The US Coast Guard said nine people remain unaccounted for.

The ‘Conception’ commercial scuba diving boat was anchored off Santa Cruz Island, around 145km off Santa Barbara, when the fire broke out just after 3am on Monday.

There were 39 people on-board.

It was on the last day of a three day expedition to the Channel Islands National Park when the blaze erupted.

The Conception dive boat engulfed in flames off the Southern California Coast, 02-09-2019. Image: Santa Barbara County Fire Department

This morning, Coast Guard Lieutenant Commander Matthew Kroll said authorities had recovered 20 bodies.

He said five more had been discovered but can’t be recovered due to unsafe conditions under the boat.

He confirmed that four bodies, recovered during the initial rescue attempt, had injuries consistent with drowning.

Santa Barbara County Sheriff Bill Brown said it is not clear when authorities will be able to recover the bodies under the boat.

“It's upside down in relatively shallow water with receding tides that are moving it around,” he said.

Family Members looking for information about their loved ones are encouraged to contact this number. (833) 688-5551

— USCG Southern California (@USCGSoCal) September 2, 2019

Five crew members who were awake on the upper deck when the fire broke out were able to escape by jumping into an inflatable boat.

They made their way to a nearby boat, the Grape Escape, at around 3:30am.

The owner of the boat, Bob and Shirley Hansen, said two of the crew went back to look for survivors – but found no-one.

“I could see the fire coming through holes on the side of the boat,” Mr Hansen told The New York Times.

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

“The fire was too big; there was absolutely nothing we could do.”

42-year-old Orlando Aldana from Santa Barbara lights candles in honour of the victims of teh dive boat fire in Santa Barnara, 02-09-2019. Image: AP Photo/Stefanie Dazio

Authorities will continue to search for the nine people who are still missing, although they have warned that they are preparing for the “worst outcome.”

Records show inspections of the Conception conducted last February and in August 2018 found no deficiencies.

Main image shows a firefighter trying to extinguish a boat fire near Santa Cruz Island, California, 02-09-2019. Image: Ventura County Fire Department