20 Bodies Found, 14 Missing After Calif. Boat Fire — What Could Have Caused 'Mariner's Worst Fear'?

Speculation continues to build about the commercial diving boat that went down in flames in California early Monday, killing at least 24 people on the tail end of a Labor Day weekend excursion.

A total of 39 people — 33 passengers and six crew members — were onboard the 75-foot Conception boat when the flames erupted just after 3 a.m. while all but five crew members were asleep below deck. Those five crew members managed to jump ship and seek refuge on a nearby boat called the Grape Escape, which they traveled to via dinghy.

Santa Barbara County’s Sheriff-Coroner Bill Brown said at a press conference Tuesday that 20 bodies, 11 female and nine male, were recovered Monday, and have been brought back to the coroner’s bureau.

An additional four to six bodies were seen by search and rescue divers, though the positioning of the sunken boat made them unable to reach the victims by nightfall.

U.S. Coast Guard Captain Monica Rochester said at the same press conference that the Coast Guard has suspended search and rescue efforts pending further developments, and will instead turn their focus to recovery missions.

The cause of the fire remains under investigation by the Coast Guard and the National Transportation Safety Board, though naval architect Charles Cushing tells PEOPLE the devastating blaze could have been sparked by any number of factors.

“I don’t know the details of it, but fires can be caused by escaping gas, for example, or from cooking devices or from electrical faults, or even from lithium batteries on computers,” says Cushing, of the New York-based naval architecture, marine engineering and transportation consulting firm C. R. Cushing & Co. “There are numerous possible causes, and fire at sea is a mariner’s worst fear.”

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Speculation regarding air tanks and their possible involvement emerged in the immediate aftermath, though Cushing says the tanks, while likely full, would not have been stowed below deck, but on the top deck, where they’d be more easily accessible to divers.

“Because it’s air, of course conflagration would be just as it would be in a normal atmosphere,” he says. “If any of those oxygen bottles failed, it would still be a horrendous thing because the air is under pressure, so it’s feeding the flames rather intensely, but not in the same way as if it was pure oxygen.”

It remains unclear just what the escape routes were for the passengers below deck, though a distressing mayday call revealed that the dispatcher made several references to the group being “locked” inside the boat.

According to Brown, the below deck section of the boat had a stairwell and an escape hatch, both of which were blocked by fire.

“There’s 33 people on board the vessel, they can’t get off?” the dispatcher asks, to which he receives no audible response in the audio obtained by journalist Matthew Keys. “Are they locked inside this boat?”

Only the dispatcher can be heard speaking, and it remains unclear as to whether he is repeating what he heard back to the caller, or if he is asking the questions himself. Nothing he says is affirmatively answered by the caller.

“Can you get back on board and unlock the boat? Unlock the door so they can get off?” the dispatcher asks.

He then inquires as to whether the passengers have access to equipment to help them quell the flames.

“You don’t have any firefighting gear at all, no fire extinguishers or anything?” he asks.

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Just before the audio ends, the dispatcher says, “There’s no escape routes for any of the people on board?”

U.S. Coast Guard Captain Monica Rochester said that the Conception “has been in full compliance,” though if implications that it only had one exit and no access to fire-fighting equipment are indeed true, it likely should not have been deemed safe, says Cushing.

“At the very least, what ships have are fire pumps. You can pump water, but the size of this vessel would’ve limited the requirements for fire pump and hoses to fight a little fire. But normally you have hoses already rigged and stationed throughout the vessel,” he says. “So to say we have nothing to fight the fire with is strange, but it might be that the fire extinguishers, the crew was prevented from getting to them because of the fire. I think it’s heartbreaking to think of what happened.”

Dave Reid and wife Terry Schuller, who have both traveled on the Conception in the past, told local CW affiliate KTLA that the boat’s sleeping area is “tight,” with bunk beds that are stacked next to each other.

Reid told the outlet that in order to get to the top deck, passengers must navigate a narrow stairway with only one exit.

Rochester said at the Tuesday press conference that all vessels are required to have smoke detectors, fixed and portable fire-fighting systems, and that there are no locked doors in accommodation spaces on board.

All required systems were accounted for during the boat’s last inspection in August, Rochester said, though she was unsure if the inspection was August 2018 or 2019.

Authorities have not yet identified any victims, though crew members told their rescuers that three people on board, including a 17-year-old girl traveling with her family, were celebrating birthdays, according to the Los Angeles Times.

Sheriff-Coroner Brown said that a majority of those on board were from Santa Cruz, San Jose and the Bay Area in California.

Meanwhile, Brett Harmeling identified his sister, marine biologist Kristy Finstad, as one of the likely victims.

“Thank You ALL for your unconditional love and support during this incredibly tragic time… No final word on my sister Kristy; however, it is likely she has transitioned to be with the good Lord,” he wrote on Facebook.

Brown said the bodies recovered will be identified through DNA testing, and that investigators are working with family members to obtain samples.

The Coast Guard spokeswoman said the agency is “working deliberately with the vessel owner-operator who is with us at the time.” Truth Aquatics, which owns the Conception, could not be immediately reached by PEOPLE. Representatives from the company declined to comment to other news outlets.