Four bodies have been found near the wreckage of a commercial diving vessel that caught fire early Monday morning near an island off the coast of Southern California, Santa Barbara County Sheriff-Coroner Bill Brown said during a Monday press conference. They have been identified as two adult males and two adult females.

Four other bodies were located on the ocean floor "in close proximity to the vessel" but had yet to be recovered, Brown said, adding that the boat remains unstable.

Earlier, Coast Guard Captain Monica Rochester told reporters the agency was engaging in "search-and-rescue activities." The agency was "conducting shoreline searches for any available survivors," Rochester said during an earlier press conference.

Santa Barbara County police say four bodies have been found near the wreckage of the boat that caught fire off the coast of Southern California https://t.co/aRe1zKZcpP https://t.co/H9n7JKbYS7 pic.twitter.com/bXUB0n1fiK — CBS News (@CBSNews) September 2, 2019

The diving vessel's five crew members were rescued by a pleasure craft named the Grape Escape, Rochester said. The passengers were asleep below deck when the fire broke out, she said.

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The FBI was assisting with the investigation into the deadly fire, CBS News chief justice and homeland security correspondent Jeff Pegues reports. The bureau has an underwater search and evidence recovery team available to authorities.

The 75-foot vessel sank about 20 yards offshore from Santa Cruz Island, which is located off of Santa Barbara, Rochester said. The water was 64 feet deep, she said.

In response to a question about whether the vessel's operator had any history of violations, Rochester said the vessel had been in full compliance. The island was part of Channel Islands National Park, and the vessel was authorized to operate in the park, Chief Ranger Mark Hnat told reporters.

The Coast Guard heard a mayday call around 3:30 a.m. that the vessel was engulfed in flames, Rochester said. Santa Barbara County Fire Department spokesman Mike Eliason said on Twitter the vessel caught fire while it was anchored near the island.

The diving vessel's crew jumped into the water to escape the fire, Rochester said. They were already awake and on the vessel's bridge, she said.

Rochester identified the vessel as the Conception, which is owned by Truth Aquatics. The company told CBS News it didn't have a statement on the fire at this time.

Worldwide Diving Adventures, a company based in Santa Cruz, California, chartered the vessel for Labor Day weekend, according to the company's website. The vessel was expected to return to port Monday evening.

The U.S. Coast Guard launched several boats to help more than 30 people "in distress" off the coast of southern California. Ventura County Fire Department

April Siese and Peter Martinez contributed to this report.