One person has died and three others are still missing after a boat carrying 20 people capsized and sank near Alcatraz island, home to the famous former prison in San Francisco Bay. Rescue operations involved divers and helicopters, and fire chief Dean Crispen said crews responded to a report of "a boat on fire, 600 yards (548 metres) off Alcatraz" Island at around 3.35pm local time.

Authorities updated the initial number of missing people from two to three after hearing from witnesses. Rescuers tried to resuscitate the person who died. "They immediately initiated CPR, transported that patient to the shore. They were declared deceased," Crispen said.

“Right now we are in full rescue mode,” Crispen said, adding that three people who suffered injuries falling from the boat were taken to a hospital and expected to be released Tuesday night.

Videos of the scene showed boats deployed to rescue people who had been on the vessel, which was largely submerged with objects floating nearby.

The boating mishap was initially reported as a fire, “but we now don’t have any evidence of that,” Crispen said. The person who died was alive when plucked from the frigid waters by rescue crews but later died. A dog onboard also died.

Alcatraz Island was once a federal prison infamously inescapable due to the strong ocean currents and cold Pacific waters that surround it. It is now a tourist destination. It is located in San Francisco Bay about a mile (about 1.6 kilometers) north of the city’s shoreline, in an often windy area that attracts sailboats and other recreational vessels.