What we know about the Santa Cruz Island boat fire disaster

The U.S. Coast Guard was involved in a massive rescue operation Monday morning after a 75-foot commercial diving boat caught fire off the coast of Ventura County, trapping dozens of people.More than 30 people were missing and officials said some died. Many on the boat, which was off Santa Cruz Island, were believed to be sleeping below deck when the fire broke out and appear to have been trapped. (Photo courtesy Ventura County Fire Dept.) less The U.S. Coast Guard was involved in a massive rescue operation Monday morning after a 75-foot commercial diving boat caught fire off the coast of Ventura County, trapping dozens of people.More than 30 people ... more Photo: Ventura County Fire Department Photo: Ventura County Fire Department Image 1 of / 34 Caption Close What we know about the Santa Cruz Island boat fire disaster 1 / 34 Back to Gallery

Around 3:30 a.m. on Labor Day, the U.S. Coast Guard responded to a mayday call from the dive boat Conception off Santa Cruz Island in Southern California. They found the vessel completely ablaze.

The Coast Guard says five crew members on the bridge at the time of the fire were rescued by a passing good Samaritan vessel, but 34 others, most of whom were sleeping below deck, were not accounted for at the time of the initial rescue efforts.

Twenty-five bodies had been located as of Monday night, the Coast Guard said. Rescuers initially recovered four bodies, and 16 others were pulled from the water later in the day. Five others have been found but not recovered due to unsafe conditions under the boat.

Nine more people are still unaccounted for, with authorities searching through the night.

According to the Coast Guard, the boat sank in 64 feet of water while crews were fighting the fire. It was 20 yards from the shoreline of the island in the Channel Islands.

"This is probably the worst case scenario you can have," Santa Barbara County Sheriff Bill Brown said. "It's a vessel on the open sea in the middle of the night, its 3:30 in the morning ... The sleeping compartment is on the bottom of the ship and they would be sound asleep ... You couldn't ask for a worse situation."

Here's what we know so far:

— The commercial scuba diving vessel Conception was on a three-day Labor Day excursion. The trip afforded divers the opportunity to visit the Northern Channel Islands.

"On the Labor Day trip, divers have the unique opportunity to explore the pinnacles of San Miguel Island," the ad on Worldwide Diving Adventures reads. "The beginning of September is the best time to be at San Mig, which see strong winds and swell during much of the year."

— The boat is owned by Truth Aquatics, based in Santa Barbara, but was chartered by Worldwide Diving Adventures, a Santa Cruz-based company that provides "exotic dive trips, scuba instruction, and local boat diving in Monterey and the Channel Islands."

The contact information for the Northern Channel Islands trip points to Dan Chua, one of three family members listed on the Worldwide Diving Adventures site. The adventure company was founded in 1972 by Bill Finstad in Santa Cruz. The site says his daughter Kristy and her husband, Chua, both licensed scuba instructors, lead excursions.

— Kristy Finstad is believed to have been on board the Conception. On Tuesday, her brother posted on Facebook: "No final word on my sister Kristy; however, it is likely she has transitioned to be with the good Lord."

— Pacific Collegiate School, a 7th-12th grade public charter school in Santa Cruz, says two students were on board. It is not known if they survived.

— Santa Barbara County Sheriff Bill Brown said in a press conference Tuesday that the majority of the victims "appear to have been from the Santa Cruz, San Jose, Bay Area region."

— TripAdvisor photos of a Truth Aquatics' dive boat bunk room show the quarters customers would have used during overnight stays. Beds are stacked two or three tall with curtains for privacy.

BREAKING Listen to the Mayday Call from the Diving Boat that caught fire off of the coast of Southern California. @nbcbayareahttps://t.co/pldCktQvGq pic.twitter.com/qCK0V1yXVl — John Zuchelli (@tvzuke) September 2, 2019

— Emergency dispatch audio from the moments after the fire broke out can be heard above. A Coast Guard dispatcher can be heard asking, "Can you get back onboard and unlock the boat?" The crewmember's response cannot be heard. Someone can be heard saying, "I can't breathe" amid heavy static.

— There is a question of whether or not the Conception had an emergency escape hatch. The Coast Guard dispatcher asks if there is one on the boat, but an answer isn't given. Captain Monica Rochester with the US Coast Guard said a boat of that design "usually requires" an emergency escape hatch from the sleeping quarters up to the main deck.

— The Conception left from Santa Barbara Harbor early Saturday morning and was set to return at 5 p.m. Monday.

— The cause of the fire is not known at this time. The vessel has sunk and is on the ocean floor.

Katie Dowd is an SFGATE Senior Digital Editor. Contact: katie.dowd@sfgate.com | Twitter: @katiedowd