At least three people were killed when a boat overturned near San Diego on Monday as the Coast Coast and sheriff’s deputies launched a frantic search for more victims, authorities said.

In addition to the three fatalities, at least four other people “were transported to our local hospitals by ambulances,” Encinitas Deputy Fire Chief Jorge Sanchez told NBC News.

A person on the panga boat told rescuers there were 18 people on board, but it wasn’t immediately clear how many might still be missing or if any made it safely to the shores of Torrey Pines State Beach on their own, Sanchez said.

“We’re just doing our due diligence by checking if there’s anybody else in the waters,” he added. “And to this point, I don’t have anything else to report, as far as missing or accounted for.”

The U.S. Coast Guard said in a statement that there are nine “missing individuals” following “a report of an overturned vessel” in the waters off Del Mar.

San Diego Sheriff’s deputies are also assisting in the “maritime event on the beach near the 200 block of Stratford Court, the law enforcement agency said.