SAN DIEGO – Orange County health officials warned that 1,500 gallons of diesel fuel that spilled in the ocean today could be heading south, putting San Diego County beaches at risk for contamination.

The mishap was reported to San Diego authorities at 8:20 a.m., San Diego County sheriff's Lt. Dennis Brugos said.

The spill occurred when a 58-foot commercial fishing boat overturned and sank about two miles off San Clemente, said Orange County sheriff's Lt. Ted Boyne.

Boyne said the four people on the boat were treated for mild hypothermia. The emergency was reported about 3 a.m., he said.