Santa Barbara County Sheriff Bill Brown told reporters that all the victims sleeping in tight quarters below deck around 3:15 a.m. Monday had signs of smoke inhalation and a preliminary examination shows they died before being burned.
The fire is believed to have killed 34 people, but the remains of one of the crew members has yet to be recovered. The other five crew members who were above deck survived the fire by jumping overboard and say they tried to save the victims.
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Brown says there are no plans to conduct traditional autopsies, with a pathologist convinced smoke inhalation is the primary cause of death, but examiners will make a final determination.
The sheriff says there are multiple investigations into different aspects of the fire but it hasn't become a criminal probe.
AIR7 HD was over the scene near Santa Cruz Island where recovery efforts continued Friday.
VIDEO: Divers continue to search for evidence, remains in Santa Barbara boat fire
U.S. Coast Guard officials said the vessel was inverted underwater and must be turned over before being raised.
"Salvage operations can take some time. It is a very exacting, tolling process on the folks that are on scene, the divers that have to assist, and the continued assessment and rigging of the vessel," Coast Guard Capt. Monica Rochester said Friday. "So it's not a hurry up and lift and be placed on the barge. It's an incremental effort to make sure that we try our deliberative best to keep the vessel in tact for further investigation requirements."
Brown released the names of nine of the victims. He said the victims' identifications require DNA analysis because of the fire's intensity. Brown added that the families of all 34 victims have been contacted to collect DNA samples.
The victims whose identities were released include:
Raymond "Scott" Chan, 59, of Los Altos
Justin Dignam, 58, of Anaheim
Daniel Garcia, 46, of Berkeley
Marybeth Guiney, 51, of Santa Monica
Yulia Krashennaya, 40, of Berkeley
Alexandra Kurtz, 26, of Santa Barbara
Caroline McLaughlin, 35, of Oakland
Ted Strom, 62, of Germantown, Tennessee
Wei Tan, 26, of Goleta
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Officials say determining the cause could take a year or more.
The National Transportation Safety Board said it is coordinating a "very lengthy, detailed and comprehensive investigation" that involves tracking down inspection records and other documents, interviewing crew members and witnesses and filming the submerged wreckage of the Conception before it can be brought back to the surface.
Determining what made the boat catch on fire and then sink could take an estimated 12-18 months, said NTSB official Jennifer Homendy.
"I am 100% confident that our investigators will determine the cause of this fire, why it occurred, how it occurred and what is needed to prevent it from happening again," said Homendy.
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In the meantime, the agency expects to issue a preliminary report in just 10 days that will review the basic facts of the case, without drawing conclusions about the cause.
One initial finding, though, has already been released.
Results of alcohol testing on four of the five surviving crew members came back negative, U.S. Coast Guard officials confirmed Wednesday. One crew member was being transported to the hospital during the testing and was expected to be tested at a later time.
Results of tests for drugs were still pending, officials said.
The wreckage of the boat is submerged in 60 to 65 feet of water and inverted. Investigators are taking photos and videos of the wreckage before an attempt is made to bring it back to the surface.
Investigators believe vital evidence may have gone down with the ship or drifted out to sea.
They will look at the ship's layout and whether the bunk room below deck was too cramped and had enough exits. They'll also review maintenance records, even study photos and videos from people who have been on the boat to look for valuable evidence.
The deadly fire, which is being investigated with help from the FBI and Bureau of Alcohol, Tobacco, Firearms and Explosives, is being treated as an accident and there's nothing to suggest anything "nefarious," said Santa Barbara County Sheriff Lt. Erik Raney.
REMEMBERING THE VICTIMS
Portraits emerged Tuesday of some of the victims, including high school students, a science teacher and his daughter, an adventurous marine biologist and a family of five celebrating a birthday.
A candlelight vigil was held in Long Beach Thursday evening for those killed.
And in Santa Monica, hundreds of people joined Heal the Bay and members of the local diving community for a vigil and fundraiser for the family, friends, and community of divers affected by the tragedy.
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"As far as me, I'm a part of the community. It's a big loss," said Jon Ford, with the Santa Barbara County Fire Department. "My child that's right over there was on that boat this summer with our Junior (Coast) Guard and I don't think twice. This is a very safe operation, very professional operation."
At the marina in Santa Barbara, a memorial featuring a candle for each of the 34 victims is growing. Family members and friends of the victims gathered to mourn and to seek information.
"She's gone. She's not going to come back," said Claire, a woman who said her older sister was a member of the crew and did not survive. "I texted her yesterday. Even though I knew she wasn't going to respond, just hoping that maybe there was a slight chance maybe she would respond."
"She unfortunately left this earth doing something she loved. She was an amazing person. She had the biggest heart. She was my role model, my big sister. She was everything to me. And she's just gone now."
VIDEO: Victims of deadly boat fire remembered with waterfront memorial
The Associated Press and City News Service contributed to this story.