ENCINITAS, Calif. — A woman was killed and four people were injured — two critically— after a cliff collapsed on a popular Southern California beach Friday, authorities said.

The sandstone bluff gave way shortly before 3 p.m. in Encinitas, a suburb north of San Diego. The area is highly popular with local residents, surfers and vacationers.

The beach was filled with people at the time of the collapse. A KNSD-TV helicopter captured footage of beach chairs, towels, surf boards and beach toys strewn about the sand.

Two people were flown to hospitals in critical condition, and two were treated for minor injuries, Encinitas Fire Chief Mike Stein said. Authorities did not release their names or ages.

Homes on top of the bluff were not in any danger, Stein said. Rescue crews were searching for additional victims, but they did not have full access because of safety concerns.

Bluffs give way four to eight times a year in Southern California, but “nothing of this magnitude,” said Brian Ketterer, southern field division chief of California State Parks.

“This is a naturally eroding coastline,” Encinitas Lifeguard Capt. Larry Giles said. “There’s really no rhyme or reason, but that’s what it does naturally. …. This is what it does, and this is how are beaches are actually partially made. It actually has these failures.”

Suburbs north of San Diego have contended with rising water levels in the Pacific Ocean, pressuring bluffs along the coast. Some bluffs are fortified with concrete walls to prevent multimillion-dollar homes from falling into the sea.

The collapse occurred near Grandview Beach. It is fairly narrow, with tides high this week. Surfers lay their boards upright against the bluff.

Tourists stand on top of the cliffs for better views.

Long stretches of beach in Encinitas are narrow strips of sand between stiff waves and towering rock walls. People lounging on beach chairs or blankets are sometimes surprised as waves roll past them and within a few feet of the walls.

Some areas are only accessible by steep wooden stairs that descend from neighborhoods atop the cliffs.