OXNARD, Calif. — It was the last night of a Labor Day weekend dive trip to the idyllic Channel Islands, a pristine national park off the coast of Southern California.

Anchored in a harbor just 20 yards from the shore of Santa Cruz Island, three of the 33 guests aboard had celebrated their birthdays at dinner that night, and a crew member went to bed late after doing the dishes. He woke up just a few hours later to the sound of a pop in the dark, thinking someone was up and stumbling around. Instead, he opened a door to find the ship around him bathed in an intense orange glow, completely aflame, he recounted to a nearby boater after fleeing the ship.

There was a fire burning uncontrollably in the galley of the 75-foot Conception just after 3 a.m. on Monday, a blaze that would consume the boat, which was filled with divers on a private excursion and the tanks of air they used to explore the depths. The guests, sleeping tightly packed in stacks of bunk beds below, were trapped. Five of the crew members were able to escape into the waters near the shores of Santa Cruz Island, but authorities fear the rest were lost.

Authorities recovered 20 bodies and are still searching for unaccounted victims after a diving boat caught fire in Oxnard, Calif., on Sept. 2. (Reuters)

Emergency officials said Tuesday that they had recovered 20 bodies from the wreckage and that 14 people were still unaccounted for and were presumed dead, among them one crew member. Of those, Santa Barbara County Sheriff Bill Brown told reporters Tuesday that divers had found but not yet recovered four to six bodies around the boat’s wreckage.

“Fire is the scourge of any ship,” he said. “To be in a remote location, have a fire that occurs and have limited, if any, firefighting capabilities, and then have, all of a sudden, a fire that spread very, very rapidly — you couldn’t ask for a worse situation.”

After burning, the boat sank in about 65 feet of water, its bow exposed above the water.

U.S. Coast Guard Capt. Monica Rochester said Monday that the search would continue through the night, but she added a word of warning: “I think we all need to be prepared to move into the worst outcome.” The search was suspended Tuesday.

The five crew members who paddled away as the ship went up in flames banged on the hull of a nearby boat seeking help, and one crew member recounted the story to a couple on board. It was not immediately clear why the crew had been unable to rescue the passengers.

The crew put out a mayday alert from the smaller ship, while they could feel the heat and hear the pops of small explosions from the divers’ tanks on the Conception. Two crew members went back in an inflatable boat to search the water for survivors. And the Coast Guard began searching the area, hoping that some of the passengers might have been able to make the short swim to shore.

But as morning turned to day, and day again to evening without a sign of any of the other 26 people on board the ship, a grimmer reality set in. The fire is likely to be one of the largest recreational maritime disasters in recent memory. Officials have not yet said what sparked the blaze or what made it so deadly.

Shirley Hansen, 73, was asleep with her husband in their boat, Grape Escape, just a few hundred yards away, when they heard banging on the hull. They found five men, the crew from the other ship, shirtless to their waists, in an inflatable boat, seeking refuge.

One of the men told her a 17-year-old girl on board was among those who celebrated a birthday that night.

“We felt so helpless because you’re just sitting there,” Hansen said. “We did what we could, but to watch, and you know there are 34 people over there, and there is nothing you can do to stop the flames.”

The men, she said, were in tears.

The efforts the crew made to put out the fire on the ship before escaping were not immediately clear. Hansen said that one of the men had a broken leg after jumping from the ship’s bridge to the deck as he fled.

The dive boat, Conception, had been on a “liveaboard” trip to the scenic waters around the islands for the weekend, where divers could eat, sleep and relax in between days of dives.

A California-based dive company that had chartered the ship for the Labor Day weekend advertised that it would be a fun-filled journey.

“Nutrient rich waters bathing this island bring BIG fish: halibut, bugs, rockfish, wolfeels, lingcod,” the description said. “The precipitous geology at Boomerang, Skyscrapers, Richardson’s and Wilson’s Rock will blow you away. The island also hosts pristine shallow reefs hosting an incredibly diverse collection of sea life. Night dives are delightful; octopi roam the reefs and bioluminescent zooplankton flash colors to silhouette the diver.”

Tickets were $665. The boat was scheduled to come back on Monday afternoon.

Conception is one of three dive boats operated by Truth Aquatics, a 45-year-old company based in Santa Barbara that has a sterling reputation among the local diving community. A person who answered the phone at the company’s office in Santa Barbara declined to comment Monday morning.

Coast Guard officials said they believe the ship was in compliance with all regulations, and did not have any violations of note. The Conception can sleep up to 46 people on 13 double bunks and 20 single bunks that are stacked two and three high, and has a large galley and a pair of air compressors to fill the divers’ tanks.

The diving tanks — usually filled with compressed air or a nitrogen/oxygen mix known as nitrox — might have fueled the fire; Hansen said that she heard and saw the explosive bursts each time a tank exploded on the boat.

Andy Taylor, owner of Blue Water Hunter scuba certification in Santa Barbara, said that he had several friends who were on the Conception over the weekend, but he has yet to hear what happened to them.

“We’re all just waiting,” he said.

The Conception was stolen in 2005 by a homeless man, who after unmooring it, motored north to an Air Force base where he ran it aground. The boat underwent a more than $1 million refurbishment after the wreck, making it among the most modern in the local dive fleet. Taylor said the ship’s captain was known for his trustworthiness.

“Our hearts are with the families and loved ones affected by this tragic incident,” California Gov. Gavin Newsom (D) said in a statement. “As we wait to hear more, we are eternally grateful for our heroic first responders that are on site — working to ensure every individual is found.”

Police divers from multiple law enforcement jurisdictions in Santa Barbara, Ventura and Los Angeles counties scoured the wreckage for bodies while other emergency crews searched the land around the site for survivors. By 7:30 p.m. Eastern time, they had not announced any survivors beyond the five crew members.

The fire is likely to increase scrutiny on the safety of dive and other touring boats. Sen. Dianne Feinstein (D-Calif.) called for a federal investigation.

“We must know what fire-suppression systems and other emergency equipment are in place on these boats and whether they were in working order on the Conception,” she said in a release. “And we need to understand exactly how the crew was trained and, if they were awake and above-deck, why they were unable to alert or help rescue passengers. A tragedy of this nature is simply unimaginable.”

An average of about 650 people die each year in boating accidents, according to statistics from the Coast Guard from the past 20 years. The majority of those are from collisions with other boats or other objects, with operator inattention and improper lookout as the two primary factors investigators have assessed in accidents. But serious problems from fires are less common. According to Coast Guard data, four people died in 256 fire incidents in 2018, and all of those were from fires that stemmed from fuel explosions.

The National Transportation Safety Board said it was sending a team to California to investigate the fire, and the FBI was also involved.

Hansen said that one of the crew members told her his girlfriend was sleeping beneath the deck with the other guests.

“If more people had gotten off that boat,” she said, pausing, “we had room for them.”

Alice Crites contributed to this report.