Three people are dead and at least seven more are missing after a small boat overturned off the coast near San Diego, California, officials said.

At least 16 people, including two children, were on board the panga-style fishing boat, the US Coast Guard said. Initially, as many as nine people were reported missing - but two were later found and detained.

An official told CBS News, the BBC's US partner, that the incident was being treated as a suspected case of human smuggling. A number of Indian passports were found near where the boat washed up on a beach, news agency Reuters reported.

Four of those found have been taken to hospital. It is not known if anyone else entered the water.

The coast guard said on Tuesday that seven people from the boat remained missing, but that it had suspended its search "pending further developments".

Search and rescue efforts by air and sea had continued for nearly 28 hours, covering more than 520 sq nautical miles, the agency said.

It was unclear where the boat was coming from before it flipped about 35 miles (56km) north of the Mexico border, Coast Guard Petty Officer Chris Sappey told the Associated Press news agency.

He said similar vessels were commonly used by smugglers. "They were not tourists," Mr Sappey said. "They are believed to be migrants."

A panga boat is a small, open lightweight vessel typically powered by an outboard motor.

A coastguard cutter and a helicopter were searching for the missing, a spokesman told the BBC.

Nick Backouris, a lieutenant with the San Diego Sheriff's office, said people from his office helped victims on the beach.

"A doctor hiking nearby called in and said, 'I see people doing CPR on the beach, I'm running that way,'" Backouris told AP. "The deputies were assisting with life-saving measures."

Jorge Sanchez, of the Encinitas Fire Department, said the immigration status of those caught was not known.