Crew members on an ill-fated California dive boat that killed 34 people after catching fire off the coast of Santa Barbara last year said they weren’t given proper emergency procedure instructions, according to documents released by the National Transportation Safety Board Wednesday.

While NTSB investigators said the cause of the fire is still undetermined, Ryan Sims, who had only worked on the boat for about three weeks before the fire, later told investigators he remembered “seeing sparks” when he plugged his cell phone in before going to bed.

The five crew members sleeping on the top deck of the 75-foot, three-deck Conception were forced to leap from the boat into the water in the predawn hours of Labor Day 2019 when they suddenly awoke to flames. They were the only survivors; All 33 passengers and one crewmember sleeping below deck were killed in the fire.

He said that morning “while still in a sleep-like state, he had heard a pop and then a crackle downstairs,” and a crew member yelling “Fire! Fire!”

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“I didn’t know what the procedures were supposed to be,” Sims told investigators. He said the day before the fire the captain told him they would go over emergency procedures when they “have time.” Other crew members agreed they weren’t well versed in safety procedures.

The Conception is engulfed in flames after a deadly fire broke out aboard the commercial scuba diving vessel off the Southern California Coast. The crew aboard a Southern California scuba dive boat had not been trained on emergency procedures before the deadly fire broke out last year, killing 34 people in one of the state's deadliest maritime disasters, according to federal documents released Wednesday, Sept. 16, 2020. (Santa Barbara County Fire Department via AP, File)

They said they tried to go below deck to save the passengers but flames blocked their way.

Capt. Jerry Boylan said he made a mayday call at 3:14 a.m., saying, “I can’t breathe,” before abandoning ship.

They got into a nearby boat, whose captain kept calling for help as Conception crew members returned to search for survivors. It took more than an hour after Boylan's first mayday call for the Coast Guard and other boats to arrive. The Conception sank just after daybreak.

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“I came out of my room and tried to enter the galley which was completely engulfed in flames,” galley hand Michael Kohls said. He told investigators he had been woken by a scream, the Times reported. “I called out ‘FIRE’ to everyone on board. I had to jump over the side railings to reach the galley because the flames had surrounded the wheelhouse.... We could not reach any of the passengers who were cut off to us on the other side of the galley.”

The NTSB documents said that “numerous electronic devices” were being charged in the salon on the boat’s main level the night before the fire. “It is therefore reasonable to include lithium-ion battery failure as a possible ignition source in this fire scenario,” the report stated. “Another potential source of ignition is the vessel’s electrical system in the salon compartment.”

An earlier investigation found the crew was in violation of a requirement to have one roving night watch awake at all times. Glen Fritzler, the owner of Truth Aquatics, which operated the Conception, has said the crew was awake and has denied any wrongdoing, according to the Times.

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Boylan could face federal manslaughter counts, and recent court documents say criminal charges are imminent.

Coast Guard investigators who examined the Vision -- an identical boat -- after the fire found 19 electrical deficiencies. “Cable runs were not enclosed in protective conduit, were often not supported, and did not have the appearance of a professional installation,” the NTSB report said, according to the Times.

Fritzler has previously said he believed lithium-ion batteries may have been the cause of the fire and said he wasn’t warned of the danger by the Coast Guard, according to the newspaper.

Families of 32 victims also have filed claims against Glen and Dana Fritzler and Truth Aquatics. In turn, the Fritzlers and the company have filed a legal claim to shield them from damages under a maritime law that limits liability for vessel owners. Court filings show they have offered to settle lawsuits with dozens of victims’ relatives.

An attorney for nine families who lost people in the fire said he would be reviewing the NTSB documents. “We will hold those responsible for this disaster fully responsible,” he said, according to the Times. “It is premature to reach conclusions. We are going to be analyzing it in the days ahead with legal and technical experts.”

Coast Guard records show the Conception had passed its two most recent safety inspections.

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The NTSB plans to hold a public hearing on Oct. 20 to announce its findings.

The Associated Press contributed to this report