Heavy downpours struck before dawn on Tuesday after thousands of residents in Santa Barbara County along the Pacific coast north of Los Angeles were ordered to evacuate. But only 10 to 15 percent complied with mandatory orders, said Amber Anderson, a spokeswoman for the Santa Barbara Fire Department.
Emergency workers, using search dogs and helicopters, have rescued dozens of people stranded in rubble, Anderson said.
The mudslide toppled trees and demolished cars and covered blocks of quiet residential neighbourhoods with a thick layer of mud, Santa Barbara County Sheriff Bill Brown said at a news conference.
"The best way I can describe it is it looked like a World War One battlefield," Brown said.
The death toll on Tuesday surpassed a California mudslide on Jan. 10, 2005, that killed 10 people as a hillside gave way in the town of La Conchita, less than 20 miles (32 km) south of the latest disaster.
Last month's wildfires, the largest in California history, left the area vulnerable to mudslides. The fires burned away grass and shrubs that hold the soil in place and also baked a waxy layer into the earth that prevents water from sinking deeply into the ground.
The overnight rains forced road closures, including a 30-mile (48-km) stretch of U.S. Highway 101, essentially cutting off traffic between Santa Barbara and Ventura counties northwest of Los Angeles.
(Additional reporting by Peter Szekely in New York, Chris Kenning in Chicago, Steve Gorman and Dan Whitcomb in Los Angeles and Brendan O'Brien in Milwaukee; Editing by Leslie Adler and Lisa Shumaker)
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)