SAN DIEGO -- A 20-foot boat suspected of being used for illegal immigrant smuggling washed ashore in La Jolla early Wednesday, authorities said.

A transient reported that the vessel ran aground on the beach just south of the Children's Pool lifeguard tower about 4:20 a.m., according to the San Diego Lifeguard Service.

The witness also said about 10 people dressed in black fled from the boat when it hit the rocky reef area, said lifeguard Lt. Andy Lerum, adding that none of them were immediately tracked down.

Lifejackets, fuel tanks filled with gasoline and water bottles with Hispanic logos on them led authorities to suspect that the damaged, unregistered vessel is "a likely smuggling boat," Lerum said.

The U.S. Coast Guard was investigating the incident, he added.