The Conception was pulled from the water two weeks ago and taken to Naval Base Ventura County in Port Hueneme.
The ATF continues to investigate the origin and cause of the fire, Colbrun said.
The National Transportation Safety Board is also looking into the fire and its investigation is still in the fact-finding phase, spokesman Eric Weiss told CNN. The NTSB’s report could take several months to complete, he said.
The Conception caught fire around 3:14 a.m. on Labor Day off Santa Cruz Island, about 20 miles away from the coast of mainland California. It was the last day of a three-day diving trip.
By 7:20 a.m. local time, the ship began to sink in 64 feet of water. The boat had burned down to the water line, Santa Barbara County fire spokesman Mike Eliason said in the days after the tragedy.
Ventura County firefighters reached the boat within 15 minutes, the fire department said. But by then, it was engulfed in flames.
Firefighters struggled to extinguish the fire because each time it was snuffed out, flames flared back up — perhaps because of the fuel on board, the Coast Guard’s Aaron Bemis said.
The Conception was not required to have a “black box” on board and was not voluntarily fitted with a black box, an NTSB official said during its first days on the scene.