Three people were killed and two more injured after a cliff collapsed onto a popular Southern California beach Friday, authorities said.

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

A woman died at the scene, and two people died at a hospital, the city reported.

Authorities did not release their names or ages.

Another person remained hospitalized and a fifth had minor injuries and wasn't hospitalized, authorities said.

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.

Surfers wait at the top of the stairs above the site of the cliff collapse. The area is highly popular with local residents, surfers and vacationers. (Denis Poroy/Associated Press)

A 9-metre-by-7-metre section of the bluff located about 4.5 metres above the beach gave way, dumping rock and sand onto the people below.

Several victims had to be dug out of the mound.

The bluff remained unstable and the area was closed. Homes atop the cliff were not in any danger, Encinitas Fire Chief Mike Stein said.

At one point, dogs were brought in to search for additional victims, but by late Friday night none had been found.

Emergency responders attend to the cliff collapse. (Paul Ecke/Reuters)

Officials said the cliff was unstable. They cordoned the area in order to keep people out of harm's way.

A skip loader was brought in to clear away the dense, heavy debris.

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 our beaches are actually partially made. It actually has these failures."

Emergency responders and a search team work at the scene of the cliff collapse. (Mike Blake/Reuters)

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 neighbourhoods atop the cliffs.