Authorities said at least 28 people were injured while 30,000 remained subject to mandatory evacuation orders.
Anxious family members awaited word on loved ones on Wednesday as rescue crews searched grimy debris and ruins for more than a dozen people missing after mudslides in Southern California destroyed an estimated 100 houses, swept cars to the beach and left at least 17 victims dead.
"It's just waiting and not knowing, and the more I haven't heard from them — we have to find them," said Kelly Weimer, whose elderly parents' home was wrecked by the torrent of mud, trees and boulders that flowed down a fire-scarred mountain and slammed into the coastal town of Montecito in Santa Barbara County early Tuesday.
"We've gotten multiple reports of rescuers falling through manholes that were covered with mud, swimming pools that were covered up with mud," said Anthony Buzzerio, a Los Angeles County fire battalion chief. "The mud is acting like a candy shell on ice cream. It's crusty on top but soft underneath, so we're having to be very careful."
Buzzerio led a team of 14 firefighters and six dogs in deep debris. They used long-handled tools to search the muck in the painstaking task.
Teams rescued three people Wednesday, but they also discovered two more bodies, raising the death count to 17, Santa Barbara County Sheriff Bill Brown said. Seventeen people were reported missing.
A dozen people were hospitalised at Santa Barbara Cottage Hospital and four were in critical condition, Dr Brett Wilson said.
"Most injuries we saw were related to fast-moving debris," Wilson said. "You can't even fathom what these poor patients went through to finally make their way to the emergency department."
The deluge destroyed 100 houses and damaged 300 others, Santa Barbara County authorities said. Eight commercial properties were destroyed and 20 damaged.
Some 500 firefighters and other rescue workers were searching debris spread across a wide swath of Montecito, a wealthy enclave of about 9,000 people northwest of Los Angeles that is home to such celebrities as Oprah Winfrey, Rob Lowe and Ellen DeGeneres.
Helicopters were used to hoist more than 50 people to safety from roofs, where they scrambled to escape the mud or because debris had blocked roads and left them stranded.
Along Hot Springs Road, where at least two homes were carried off their foundations, bulldozers cleared muck and debris from areas already searched. Utility crews began the laborious task of repairing downed power lines and snapped telephone poles.
People in Montecito had counted themselves lucky last month after the biggest wildfire in California history spared the town. But it was the fire that led to the mudslide, by burning away vegetation.
"We totally thought we were out of the woods," said Jennifer Markham, whose home escaped damage in both disasters. "I was frozen yesterday morning thinking, 'This is a million times worse than that fire ever was.'"
Only an estimated 10 to 15 percent of residents fled when ordered and much of the damage occurred where evacuations were voluntary.
Marco Farrell, a real estate agent, cited "evacuation fatigue" as his reason not to leave – a decision he wouldn't make next time. He woke to the sound of pounding rain early Tuesday and went outside to investigate.
He was two blocks from home when he heard a rumble that he realised was the mudslide he feared.
"I ran as fast I could and yelled, 'Flash flood!' as I passed neighbors' homes," he said.
Farrell warned his parents inside, and within a minute, a boulder plowed through the kitchen door. The mud flow went through the home and burst through a backdoor.
The flow was so powerful it swept several homes off their foundations, crushed others and wrapped cars around trees. At least two unrecognisably mangled cars were carried like driftwood all the way to the beach, where they were partly covered in seaweed.
A 30-mile stretch of US Highway 101 linking Ventura and Santa Barbara was still covered in heavy debris and not expected to reopen until Monday. Because of the closure, boats were used to ferry some employees to Cottage hospital.
Another storm-related death was reported in Northern California, where a man was killed when his car was apparently struck by falling rocks in a landslide Tuesday evening in Napa County.