SAN DIEGO — At least eight people were killed when two migrant smuggling boats capsized in shallow but treacherous surf amid heavy fog, authorities said Sunday, marking one of the deadliest maritime human smuggling operations ever off of U.S. shores.

A Spanish-speaking woman on one of the panga-style boats called 911 Saturday night to report the other vessel overturned in waves at Black’s Beach, authorities said. She said there were 15 people on the capsized vessel and eight on hers.

Coast Guard and San Diego Fire-Rescue crews pulled bodies of eight adults from the water, but fog hampered the search for additional victims.

Recovery efforts resumed Sunday but no additional bodies were found. The Coast Guard announced on Twitter that the search was suspended at 3:30 p.m.

Survivors may have escaped on land, including the woman who called 911. Authorities did not know her whereabouts.

San Diego Lifeguard Chief James Gartland said rescuers found the two boats overturned in shallow waters when they arrived. Surf was modest, with swells around 3 feet (1 meter), but skies were foggy and black.

“That area is very hazardous, even in the daytime,” Gartland said at a news conference. “It has a series of sandbars and in-shore rip currents, so you can think that you can land in some sand or get to waist-high, knee-high water and think that you’re able to be safe to exit the water, but there’s long, in-shore holes. If you step into those holes, those rip currents will pull you along the shore and back out to sea.”

Black’s Beach is about 15 miles (24 kilometers) north of downtown San Diego in a secluded area not far from the popular La Jolla Shores. Its reputation for some of the best breaks in Southern California draws many surfers.

Hundreds of maritime smuggling operations occur every year off California’s coast and sometimes turn fatal. In May 2021, a packed boat carrying migrants capsized and broke apart in powerful surf along the rocky San Diego coast, killing three people and injuring more than two dozen others.

Smuggling off the California coast has ebbed and flowed over the years but has long been a risky alternative for migrants to avoid heavily guarded land borders. Pangas enter from Mexico in the dead of night, sometimes charting hundreds of miles north. Recreational boats try to mix in unnoticed with fishing and pleasure vessels during the day.

South of the U.S. border, there are many secluded, private beaches with gated entrances between high-rises with magnificent ocean views, some only partially built because funds dried up during construction. Popotla, a fishing hamlet where narrow streets are lined with vendors selling a wide variety of local catch, is favored among smugglers for its large, sandy beach and relatively gentle waves.

At least some of Saturday’s victims were Mexican, according to the consulate in San Diego, but how many was unknown. Illegal crossings have soared under President Joe Biden, with many migrants turning themselves in to Border Patrol agents and being released in the United States to pursue their cases in immigration court.

A pandemic rule scheduled to end May 11 denies migrants a chance to seek asylum on grounds of preventing the spread of COVID-19 but enforcement has fallen disproportionately on Mexicans, Hondurans, Guatemalans and El Salvadorans because those have been the only nationalities that Mexico agreed to take back.

As a result, people of those four countries have been more likely to try to elude capture, knowing they are likely to be expelled under the public health rule, known as Title 42 authority. Mexico recently began taking back Cubans, Haitians, Nicaraguans and Venezuelans under Title 42.