One person has died and three others remain missing after a pontoon boat carrying mostly family members sank near Alcatraz Island in San Francisco Bay on Tuesday, prompting a large-scale search and rescue operation.
Authorities said 16 people were rescued after the vessel overturned about 600 yards from Alcatraz during what officials described as a memorial service.
Three people were taken to hospital with injuries and were reported to be in stable condition.
Emergency responders said the search for the missing continued into the evening with divers, helicopters and rescue vessels deployed across the area.
The San Francisco Fire Department received an emergency report at 3:37 p.m. local time after an initial call suggested a vessel was on fire.
Fire Chief Dean Crispen later said responders found no evidence of a fire upon arrival.
Instead, witnesses described rough seas and a boat that began taking on water before capsizing.
Authorities later identified the vessel as a three-deck pontoon boat known as Volare.
Crews found the vessel nearly submerged with its engine still running and leaking fuel.
The person who died was pulled from the water alive by rescuers but was later pronounced dead after being brought ashore.
Officials also confirmed that a dog onboard died in the incident.
Those rescued were transported to Gashouse Cove Marina before injured passengers were taken for medical treatment.
Officials said witness statements led investigators to revise the number of missing people from two to three.
The search area later expanded into open ocean west of the Golden Gate Bridge as rescue operations continued overnight.
Longshoreman Justin Marceline, who helped rescue passengers alongside fisherman Mike Montoya, described the situation as "complete chaos when we showed up".
He said many of those rescued were exhausted or struggling in the water.
Boat captain Aaron Anfinson said his vessel responded after another boater alerted them to the distressed craft.
By the time they arrived, the flames initially reported were no longer visible, but the boat was sinking and passengers were already entering the water.
Authorities said the vessel is believed to have departed from the vicinity of the St. Francis Yacht Club.
The cause of the sinking remains under investigation.