Two people were killed and 23 others transported to hospitals after a vessel overturned Sunday off the coast of the US city of San Diego, authorities said.

A US coast guard helicopter flies over the area where a boat capsized just off the San Diego coast. (Photo: Agencies)

Multiple agencies including San Diego Lifeguards rescued 25 people from the water, said the San Diego Fire-Rescue Department on Twitter.

"Sadly, two did not survive. 23 were taken to local hospitals," the department tweeted, adding that US federal agencies "are still searching the water in vessels and aircraft."

The incident was reported near 200 Catalina Boulevard around 10:30 am local time, US media reported, citing the department.