A scuba dive boat was operating in violation of Coast Guard regulations when a fire broke out killing 34 people in California, a National Transportation Safety Board (NTSB) report said.
The NTSB said that all six crew members on board the Conception were asleep when the deadly blaze broke out on September 2.
Grieving families have been left wondering if a required night watchman could have saved their loved ones following the disclosure from the board on Thursday.
The findings could help federal authorities conducting a criminal investigation into the fire, who could bring charges under a statute known as seaman’s manslaughter.
Five crew members, including the captain, were asleep on the vessel’s second deck and survived.
The sixth, a 26-year-old deckhand named Allie Kurtz, was sleeping below and perished with the boat’s 33 passengers.
Ms Kurtz’s grandmother, Doris Lapporte, said she was too distraught on Thursday to comment on the NTSB’s findings, issued days before the family planned to scatter her granddaughter’s ashes at sea.
“I have nightmares every day about her going up in flames,” Mrs Lapporte said, crying.
“This isn’t the time to talk about how angry I am or how I feel.”
Crews raised the wreckage of the burned-out boat on Thursday from waters off Santa Cruz Island, northwest of Los Angeles, where the vessel was anchored the night of the tragedy.
The Conception’s Certificate of Inspection, issued by the Coast Guard, requires a “roving patrol at all times” when passengers’ bunks are occupied.
The parents of Charles McIlvain, a 44-year-old visual effects designer who was onboard with his neighbour, said the missing roving watchman “disturbs us greatly”.
“Early detection may have made an incredible difference in outcome,” Clark and Kathleen McIlvain said in a statement.
Douglas Schwartz, an attorney for the Conception’s owner, Truth Aquatics Inc, said in a statement that a crew member was awake shortly before the fire, which started around 3am.
He said the crewman checked “on and around the galley area” around 2.30am.
The first mayday call from the captain was transmitted at 3.14am.
The victims on the Conception were a diverse collection, including a girl celebrating her 17th birthday with her parents and a friend, a marine biologist who was leading the three-day scuba diving excursion, an Indian-born dentist and her husband from Connecticut, an environmental scientist and a professional photographer.
The last of the 34 bodies was pulled from the water on Wednesday, and Santa Barbara County Sheriff Bill Brown released the names of the last seven to be identified during a news conference on Thursday.
It is believed all died from smoke inhalation.
“May they all rest in peace and may their families know that all of us who have been involved in this sad operation continue to hold them in our hearts and in our prayers,” he said.
The Coast Guard has issued additional safety recommendations in the wake of the tragedy, such as limiting the unsupervised charging of lithium-ion batteries and the use of power strips and extension cords.