The two additional fatalities were discovered as some 500 rescuers using search dogs, helicopters and thermal-imaging equipment dug through waist-deep mud for victims or survivors of the mudslides, which were triggered by a heavy downpour early on Tuesday.
Three more people were rescued from the path of debris on Wednesday. None of the dead have been publicly identified.
"We realise that this is going to be a long and difficult journey for all of us and our community," Santa Barbara County Sheriff Bill Brown told reporters at a late afternoon news conference.
The walls of mud that roared through foothills and valleys sandwiched between the Pacific Ocean and the sprawling Los Padres National Forest also destroyed 100 single-family homes, damaged hundreds of other buildings and injured 28 people, said Amber Anderson, a spokeswoman for the Santa Barbara County Fire Department.
A major north-south highway along the coast, U.S. Route 101, was closed in both directions and not expected to reopen until next week.
Among the damaged properties were historic hotels and the homes of celebrities including television personality Oprah Winfrey and talk-show host Ellen DeGeneres, who both live in the upscale hillside community of Montecito, known for its natural beauty and proximity to Los Angeles.
Verdant hillsides that had provided estates with a sense of seclusion were largely denuded by last month's historic wildfires, making them vulnerable to the massive mud and debris slides that sent boulders crashing into homes, turned highways into raging rivers and shredded cars into tangles of metal.
The sound of destruction
One resident of Toro Canyon described being awakened before dawn Wednesday when his home began shaking and he heard sounds like those of a freight train and snapping wood.
"What they were was a bunch of trees that were being snapped by the mud and boulders and debris that were sliding down Toro Canyon," Jonathan Reichlen, 45, who owns an urban landscaping company, said in a phone interview.
"I just kind of waited it out because I did not want to go down to Toro Canyon while ... the mudslide was actually going on," he said.
Reichlen said he had emergency food supplies and water but no hot food and was trying to figure out a way to get safely out of the canyon.
It was the latest blow to a region still rebuilding after the wildfires.
Officials have ordered residents in a large swath of Montecito to stay in their homes so that rescuers can better go about their work.
Helicopters were ferrying people out of the Romero Canyon neighbourhood, where about 300 people were cut off after a massive debris flow blocked the road into the area.
The mudslides closed several historic hotels, including The Four Seasons Biltmore, which had just reopened on Monday after repairing wildfire damage. The courtyard of the 90-year-old Montecito Inn, built by silent movie actor Charlie Chaplin, was filled with a thick crust of debris driven by the slides.
The disaster followed a violent rainstorm that dumped as much as 6 inches (15 cm) of water onto areas northwest of Los Angeles.
Winfrey posted videos on Instagram showing her wading through nearly knee-deep mud on her Montecito property and later inspecting the damage.
"There used to be a fence right here. That's my neighbour's house. Devastated," she said.
Talk-show host DeGeneres posted a picture of a mud- and debris-filled street outside her Montecito home on Twitter, saying she did not yet know the condition of the house itself.
Former tennis star Jimmy Connors said in a tweet that he and his wife, Patti, had been evacuated by helicopter on Tuesday from their home in the posh hillside community.
The number of fatalities surpassed the death toll from a California mudslide on Jan. 10, 2005, when 10 people were killed as a hillside gave way in the town of La Conchita, less than 20 miles (30 km) south of the latest disaster.
Last month's wildfires, including the Thomas Fire, which became the largest in California history, not only burnt away trees, grass and shrubs that held soil in place, but also baked a waxy layer into the earth that prevents water from sinking deeply into the ground.
(Additional reporting by Alex Dobuzinskis and Dan Whitcomb in Los Angeles, Sharon Bernstein in Sacramento, Gina Cherelus and Peter Szekely in New York, Rich McKay in Atlanta and Brendan O'Brien in Milwaukee; Writing by Scott Malone and Dan Whitcomb; Editing by Tom Brown and Leslie Adler)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)