Two women are dead and three other people are hospitalized after a boat at a refueling dock in Long Beach burst into flames Saturday afternoon.

It’s not yet confirmed what caused the blaze, but Long Beach Fire Department Capt. Jake Heflin said preliminary reports are the boat was in the process of or had just finished gassing up at the Alamitos Bay Fuel Dock when the blaze erupted. Fueling a boat can be dangerous if fumes are not dissipated before the engine is started.

Firefighters were just across the street at a nearby fire station when the blaze erupted at about 5:15 p.m., but the flames were so intense that the boat was already engulfed by the time they arrived, Heflin said.

Jed Gibbs, who works at the nearby Crab Pot restaurant said he heard a pop, which he assumes was an explosion, come from near the dock and then suddenly saw the thick plume of smoke.

“Out of nowhere we saw it burst into flames,” he said.

Heflin said the watercraft was a 35-foot powerboat. Everyone killed or injured in the blaze was aboard the vessel, but crews are still investigating if they were all passengers or possibly workers helping refuel.

All of the dead and injured were in their 60s, he said. The three survivors—two men and a woman—were hospitalized with burn-related injuries, according to Heflin.

“I am devastated to learn of this tragic loss of life,” Mayor Rex Richardson said in a statement on Facebook. “My thoughts are with the victims and their families.”

Monica Solorzano, who works at the Long Beach Yacht Club across the bay from the dock, said she saw the intense blaze coming from a boat at the refueling station, which is situated in the water roughly halfway between Naples Island and the San Gabriel River.

“It was a pretty big flame, lots of smoke,” she said.

More than a dozen fire engines, boats and other apparatus responded to the blaze to douse the flames. Crews towed the vessel to an isolation dock to continue their investigation, Heflin said.

City News Service contributed to this report.