U.S. authorities are conducting a criminal investigation into the fiery dive boat disaster that killed 34 people off the coast of California, two officials said Monday.

The FBI, Coast Guard and U.S. attorney in Los Angeles are overseeing the investigation, according to the two people who were not authorized to speak publicly and commented on condition of anonymity.

Federal agents on Sunday raided the office of the boat’s owner, Truth Aquatics Inc. in Santa Barbara, and its two remaining vessels.

Investigators have been gathering other evidence, including interviewing the captain and four surviving crew members, since the Sept. 2 tragedy off the Channel Islands.

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Authorities are looking into various safety issues, including whether a night watchman was on duty when the blaze broke out before dawn.

Thirty-three passengers and one crew member were trapped below deck when the fire broke out after 3 a.m. on the Conception. Efforts by the crew to save them were unsuccessful, according to authorities who spoke with them and the boat’s owner.

Santa Barbara County Sheriff Bill Brown said initial examinations indicate the people died of smoke inhalation before being burned. All but one body has been found.

High winds have postponed the search for the final victim, as well as salvaging the vessel that sits upside down in 65 feet (20 meters) of water off Santa Cruz Island.

(AP)