Investigators say that while they cannot definitively give a cause for the fire they believe that the “propensity of lithium ion batteries to overheat” sparked the 2019 blaze.
It has previously been reported that a crew member had recalled seeing sparks when plugging his phone in before bed.
Investigators say that most of the 33 passengers in the bunk room were awake and tried unsuccessfully to escape the fire through an awkward emergency hatch.
The National Transportation Safety Board say that a night watchmen could have bought the crew more time to fight the fire and evacuate the passengers.
“Had a crew member been awake, and patrolling the 75-foot-long Conception on the morning of the fire, it is likely that he or she would likely have discovered the fire at an early stage allowing time to fight the fire and give warning to passengers and crew to evacuate," investigator Andrew Ehlers reported.
“The absence of the required roving patrol on the Conception delayed detection and allowed for growth of fire, precluded firefighting and evacuation efforts, and directly led to the high number of fatalities in the accident.”
Authorities say the incident was the deadliest US marine accident in 70 years.
The preliminary NTSB report also stated that 11 months before the fatal fire another boat operated by Truth Aquatics also saw. Battery fire break out onboard.
“We've seen repeated evidence of violations with this company," said NTSB Chairman Robert Sumwalt.
Lawyers for Truth Aquatics have not commented.