LOS ANGELES (AFP) — At least eight people were killed when two suspected smuggling boats overturned off the coast of southern California, rescuers said Sunday.

It was unclear exactly what caused the nighttime accident, in an area San Diego lifeguard chief James Gartland described as “hazardous” due to sand bars and rip currents.

“We lost eight souls,” Gartland told a press conference. “This is one of the worst maritime smuggling tragedies that I can think of in California, certainly here in the city of San Diego.”

Gartland said a Spanish speaker had called the 911 emergency number just before midnight on Saturday, saying there were some 23 people between two small, open boats — eight on one vessel and 15 on another — that had overturned at Torrey Pines beach in San Diego, a city near the Mexican border.

Rescuers did not find any survivors, but some “may have left the beach” by the time the first responder teams arrived on scene, Gartland said.

All of the deceased were adults, he added, saying he had no further details on their nationalities.