Oct. 20 (UPI) -- Investigators told the National Safety Transportation Board on Tuesday that they were unable to determine a cause for a fire that killed 34 aboard a dive boat off the coast of California last year.
The officials said the boat was too damaged to pinpoint the exact location and cause of the fire after it was recovered from the sea floor. They pointed to a number of factors, though, that possibly contributed to the severe outcome of the blaze.
The officials spoke as part of an NTSB virtual hearing on the investigation of the fire, which caused the 75-foot recreational dive boat called the Conception to sink Sept. 2, 2019, Labor Day weekend.
Investigators said the blaze began in the back of the main deck salon, an area where some of the passengers had plugged in their phones and other devices to charge for the night. Some of the items contained lithium ion batteries, which can overheat and cause flames.
Such devices sparked a fire on the Conception's sister vessel, the Vision, on a previous voyage, but that blaze was quickly contained.
Though there were smoke detectors in the below deck bunk room where the divers -- and one crew member -- slept the night of the fire, there weren't any in the salon.
A crew member who was in the upper deck at the time of the fire said they observed a glow from the salon and climbed down where they saw the flames blocked access to the below deck. Authorities said the five crew members who survived the blaze had been in the upper deck and tried repeatedly to save those trapped below deck.
Many of the bodies were wearing shoes when they were found, suggesting they were awake and trying to escape. A coroner listed the cause of death for all 33 as smoke inhalation.
Investigators said the crew didn't follow regulations requiring a roving patrol at all times on vessel. One official told the NTSB that the fact that all six crew members were asleep at the time the blaze broke out "directly led to the high number of casualties."