A wooden boat, believed to be carrying migrants aiming for the United States, capsized in stormy seas near San Diego, California leaving at least four people dead, the US Coast Guard said on Saturday.

The US Border Patrol first found the boat off the Imperial Beach late Friday night.

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

The vessel likely capsized amid a strong storm which hit southern California over the weekend, prompting warnings of flash floods.

Who was on the boat?

Six people were found on the beach just before midnight, one of whom was pronounced dead. Four were hospitalized and one person was eventually handed over to the Department of Homeland Securities.

About two hours after finding the boat, authorities were alerted of someone in the water near the Imperial Beach Pier. On inspection, a Coast Guard crew found three dead people in the ocean.

As of Saturday morning, the authorities said they were still searching for anyone else who may have been on the boat.

The agency has said that some of the survivors claim to be Mexican citizens, while others have not been identified.

Thousands of migrants fleeing poverty and violence from various parts of the world attempt to enter the United States via Mexico every year. Many turn to the risky sea path to avoid heavily guarded land borders.

At least three people died in May when a boat carrying migrants capsized off the US-Mexico border. In 2023, eight people died when two boats carrying migrants approached the San Diego coast but capsized in the surf.

Edited by: Dmytro Hubenko