A wooden skiff believed to have been carrying migrants towards the United States capsized in stormy seas near San Diego, leaving at least four people dead and four others in hospital, the US Coast Guard said on Saturday.

The vessel was discovered by US Border Patrol agents late on Friday night after it washed into the surf off Imperial Beach. Six people were found on the shoreline shortly before midnight; one was pronounced dead at the scene, while another was rescued after being located trapped beneath the overturned boat.

Around two hours later, authorities received a report of a person in the water near Imperial Beach Pier. A Coast Guard team responded and recovered three individuals from the ocean, all of whom had died.

Search efforts were continuing on Saturday amid concerns that additional passengers may still be missing.

Several survivors identified themselves as Mexican nationals, while others had yet to be identified, officials said. One person was transferred to the Department of Homeland Security.

“Our crews and partner agencies responded immediately, but this case demonstrates the severe risks faced by migrants attempting to enter the United States by sea in unstable vessels,” said Coast Guard Captain Robert Tucker, commander of Sector San Diego.

Southern California was struck by a powerful storm system over the weekend, prompting warnings of flash flooding and mudslides. The craft involved was a panga — a small, open fishing boat with one or two engines that is frequently used by people-smuggling operations.

In an effort to bypass heavily fortified land borders, increasing numbers of migrants are turning to dangerous maritime routes, including those off the California coast. Pangas typically depart Mexico under cover of darkness and may travel hundreds of miles north.

There have been multiple similar incidents in recent years. In May, at least three people were killed when a panga capsized around 35 miles (56 km) north of the US-Mexico border. In 2023, eight people died when two smuggling boats attempted to land on a San Diego beach in thick fog and one overturned in the surf — one of the deadliest maritime smuggling tragedies in US coastal waters.

In 2022, a San Diego man received an 18-year prison sentence for piloting an overloaded vessel carrying 32 migrants that broke apart in heavy surf, killing three people and injuring more than two dozen.

Globally, nearly 9,000 people died attempting to cross borders last year, according to the United Nations migration agency — the fifth consecutive year in which the death toll has reached a record high. The UN Missing Migrants Project estimates that more than 24,506 people have died or gone missing in the central Mediterranean between 2014 and 2024, though the true figure is likely to be higher due to unrecorded deaths.