All six crew members were asleep when the fatal boat fire in California erupted, according to preliminary findings released on Thursday.
There were 39 people aboard the 75-foot Conception when it set off for a weekend dive trip to the Channel Islands in Southern California.
In the early hours of September 2, Labour Day, a fire broke out on the lower levels of the boat, which had been anchored just off the shore of Santa Cruz Island. Thirty-four people died.
The two-page report by the National Transportation Safety Board states that the five crew members who survived were asleep on the uppermost level when the fire began.
They told investigators that the sixth crew member, who died alongside the boat's 33 passengers, was also asleep in the bunk room on the lower deck, agency spokesman Eric Weiss said.
The report, which is the first of three the NTSB will release in their ongoing investigation, was based on witness testimonies, interviews with crew members and evidence collected on-site. It does not include causes of the fire.
Initial findings "raise the question of whether there was a roving watchman on duty," Weiss said. He emphasised that it is too early to determine whether a violation was made.
The US Coast Guard said in a statement to The Washington Post that according to its certificate of inspection, the Conception was required to have a roving watchman on duty.
The Coast Guard directed The Post to a set of government regulations that states that for a passenger vessel like the one involved in the fire on September 2, "The owner, charterer, master, or managing operator of a vessel . . . shall have a suitable number of watchmen patrol throughout the vessel during the nighttime, whether or not the vessel is underway, to guard against, and give alarm in case of, a fire, man overboard, or other dangerous situation."
Representatives of Truth Aquatics, the Santa Barbara company that operated the Conception, declined to comment when contacted directly.
Douglas Schwartz, the company's lawyer said in a statement that there is "witness testimony that seems to contradict the notion that the entire crew was asleep."
He added: "We do know that one crew member checked on and around the galley area at around 2.30am, approximately 30 minutes before the fire broke out."
The last victim from the September 2 fire was located this Wednesday, the Santa Barbara Sheriff's Office reported. DNA testing is still underway to identify seven of the 34 fatalities.
According to the NTSB report, the fire was discovered when a crew member sleeping in the upper deck was awakened by a noise and got up to investigate.
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When others were alerted to the fire, the captain sent a distress message to the Coast Guard.
Crew members tried to enter the salon and the galley compartment in the main deck, but were unable to because it was consumed by the fire.
"Unable to open the window and overwhelmed by smoke, the crew jumped overboard," the report stated.
The five crew members, including the captain, boarded a small boat before transferring to a recreational vessel nearby where they continued to signal for help.
Two from this group later returned to the vessel to search for survivors.
The NTSB will release two more reports in the next 18 to 24 months, Mr Weiss said.
The next one will be a complete factual account of what occurred and the final report will include analysis, probable causes and safety recommendations.
The Washington Post