As many as 34 people are feared dead after a dive boat caught fire before dawn Monday off the southern California coast, according to the U.S. Coast Guard.
As of midday, four bodies have been recovered, coast guard officials said.
Five crew members who jumped off the dive boat Conception were rescued, and Lt.-Cmdr. Matthew Kroll told The Associated Press the coast guard was searching for others who may have been able to escape the same way.
He added, however, that 34 were feared dead. Two of the crew suffered minor injuries, said Petty Officer Mark Barney.
"Right now they're conducting shoreline searches for any available survivors," Capt. Monica Rochester told reporters at a brief news conference in Oxnard.
She said the vessel was about 18 metres off the coast of Santa Cruz Island when the fire ignited.
Capt. Brian McGrath of the Ventura County Fire Department confirmed some deaths to The Associated Press, but said he could not give an exact number.
"Right now they're conducting shoreline searches for any available survivors," Coast Guard Capt. Monica Rochester told reporters at a brief news conference at Channel Islands Harbour in Oxnard.
"The crew was actually already awake and on the bridge and they jumped off," she said, adding they were rescued by a good Samaritan vessel called The Grape Escape.
Asked if the crew tried to help others aboard, Rochester said, "I don't have any additional information."
A woman who came to the harbour said, "My son was on that boat." She was led away by a Ventura County firefighter.
Rochester said the 20-metre commercial scuba diving vessel was anchored in Platt's Harbour, about 18 metres off the northern coast of Santa Cruz Island, when the fire ignited at around 3 a.m. local time.
She said the vessel sank in around 20 metres of water, adding its bow is still visible above the waterline.
The Conception was on the final day of a Labour Day weekend cruise to the Channel Islands when the fire erupted.
"At 3:15 this morning (PT), the Coast Guard overheard a mayday call. The call was garbled, it was not that clear, but we were able to get some information out of it to send vessels on scene," Barney said.
Rochester said that call indicated the boat was already fully ablaze.
The Conception was operated by Worldwide Diving Adventures, a respected Santa Barbara-based company that says on its website it has been taking divers on such expeditions since the 1970s.
Asked if the boat operator has a history of any violations, Rochester said, "The vessel has been in full compliance."
The National Transportation Safety said it is sending a team to investigate.
The Coast Guard said five crew members sleeping on the top deck of the 20-metre commercial scuba diving vessel were rescued by a good Samaritan pleasure craft called The Grape Escape.
The 34 others, who were sleeping below deck, have not been accounted for, Kroll said.
The Conception had departed at 4 a.m. Saturday with plans to return at 5 p.m. Monday.
Divers sleep in a single room of bunk beds, according to a diagram of the Conception posted on the website for Truth Aquatics, the Santa Barbara company that owns the ship.
The website says the vessel, launched in 1981, has rafts and life jackets for up to 110 passengers and exits on the port, starboard and bow that provide "easy water entry."
The trip promised multiple opportunities to see colourful coral and a variety of marine life.