vmargineanu/iStock(SANTA CRUZ ISLAND, Calif.) — The 36 people believe to have perished when a 75-foot charter diving boat burst into flames early Monday in Southern California were trapped in a sleeping deck when flames apparently blocked a stairway and an escape hatch, officials said on Tuesday.

The remains of 20 victims were recovered after the diving boat named the Conception caught fire off Santa Cruz Island around 3:30 a.m., Santa Barbara County Sheriff Bill Brown said at a news conference.

Capt. Monica Rochester of the U.S. Coast Guard announced Tuesday that the search-and-rescue mission has been suspended and has now become a search-and-recovery effort.

“It is never an easy decision to suspend search efforts. We know that this is a very difficult time for families and friends of the victims,” Rochester said. “We have suspended these search efforts due to no additional individuals having been witnessed entering the water.”

She said the decision to end the search for possible survivors was made after a search aircraft made one last flyover of the area where the boat is located in 65 feet of water.

There were 41 people on board the ship at the time of the incident, officials said.

Brown said that on Monday, dive teams recovered the remains of 11 women and nine men. He said four to six other victims were spotted inside the doomed vessel, but divers could not reach them before darkness fell.

He said the remains of a total of 16 victims have yet to be recovered, and some may be in a debris field the size of a half-mile on the ocean floor.

Sheriff Brown said autopsies on the victims recovered have not started, and investigators are asking family members for DNA samples to identify the victims. He said the youngest victim is believed to be 17 and the oldest victims are in their 60s.

He said the majority of the victims were from Santa Cruz in Northern California and the Bay Area.

Brown said the investigation into what caused the disaster is being handled by the Coast Guard and the National Transportation Agency.

He clarified reports the doors to the sleeping quarters were locked, saying there were no doors to the sleeping quarters, only curtains.

Brown said a stairway leading from the sleeping quarters to the upper decks was blocked by flames, as was an escape hatch in the sleeping quarters.

The sheriff said the captain and crew quarters were on the top deck of the 3-deck vessel, explaining why they were able to escape the boat alive.

He said one crew member was in the lower deck sleeping quarters when the fire broke out and is believed to be among those who died.

Rochester said the boat was required to have smoke detectors, fixed firefighting equipment in the engine room and fire extinguishers throughout the vessel, including ones at the front and rear of the boat.

She said that during the most recent inspection of the boat, all the required firefighting apparatus was accounted for.

Rochester said it remains under investigation whether the smoke detectors were working at the time of the fire and if the crew attempted to use the firefighting equipment before abandoning ship.

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