Authorities said a wall of mud and debris at least several feet high rumbled down a hillside in the community of La Canada-Flintridge, crashing into homes and cars and leaving a path of destruction in its wake.
There were no reports of deaths or injuries but residents were being told to leave as another heavy downpour was expected by early Saturday afternoon.
“There are mounds and mounds of dirt piled into homes and cars have been covered up and gone into homes,” Los Angeles County Sheriff’s spokeswoman Nicole Nishida told Reuters by telephone from the scene.
“(The cars) look like toys scattered across the road,” she said.
Authorities had no immediate count of the damaged homes but Nishida said that in the neighborhood where she was working she could count at least two homes that would have to be condemned.
“A car has gone into another residence and I’m smelling a lot of gas so I think there’s a gas leak that the fire department is trying to fix,” she said.
The mud came down on hillsides that were left barren by a massive wildfire last summer and officials had been warning that they were unstable.
Elsewhere in the Los Angeles area, flooding forced the closure of streets and at least one major freeway and overflowed curbs to wash into several businesses in Hollywood.
The National Weather Service has said that a weeklong series of storms that battered California in January were the strongest to hit the region in five years.
A silver lining has been heavy snowfall in mountain ranges that feed the California’s reservoirs, easing critical water shortages. But state water officials have been reluctant to declare the drought at an end.