Search for victims continues in mud-drenched California

At least 15 people have been killed and two dozen people are still missing after debris-laden flash floods slammed the California coast community of Montecito.

A major search-and rescue operation is underway with fears the death toll could rise as crews reach the worst-affected areas, after dozens of homes were swept away and cars buried by the powerful mud flow.

Among those affected is Oprah Winfrey, who has shared video of the damage in her backyard. 

Santa Barbara County spokesperson Amber Anderson on Wednesday said officials do not know where the missing people may be but believe they are within the debris field.

Debris flows hit early on Tuesday morning (local time) when 12 centimetres of rain fell in just an hour on hills and mountains scarred last month by the largest wildfire on record in California history.

Santa Barbara County spokeswoman Yaneris Muniz confirmed two more deaths in addition to those 13 deaths reported in the hours after the storm, bringing the death toll to 15.

She said a search of the stricken area is continuing as teams work to locate the dead, rescue others and evacuate those who were simply stuck in homes.

By Tuesday night, at least 13 people had been confirmed dead, at least 25 injured and at least 50 people rescued by helicopter, including a couple and their three children in Carpinteria. 

Most deaths were believed to have occurred in Montecito, Santa Barbara County spokesman David Villalobos said.

The wealthy enclave of about 9000 people northwest of Los Angeles is home to such celebrities as Oprah Winfrey, Rob Lowe and Ellen DeGeneres.

Winfrey's home survived the storm and slides.

In an Instagram post, she shared photos of the deep mud in her backyard and video of her inspecting the deluge in her backyard.

"What a day!" Winfrey said.

"Praying for our community again in Santa Barbara."

A mud-caked 14-year-old girl was among the dozens rescued on the ground Tuesday.

She was pulled from a collapsed Montecito home where she had been trapped for hours.

READ MORE: Miracle rescue of teen as mudslide death toll reaches 13

Read more: Miracle rescue of teen as mudslide death toll reaches 13

"I thought I was dead for a minute there," the dazed girl could be heard saying on video posted by KNBC-TV before she was taken away on a stretcher.

Twenty people were hospitalised and four were described as "severely critical" by Dr. Brett Wilson of Santa Barbara Cottage Hospital.

The mud was unleashed in the dead of night by flash flooding in the steep, fire-scarred Santa Ynez Mountains.

Burned-over zones are especially susceptible to destructive mudslides because scorched earth doesn't absorb water well and the land is easily eroded when there are no shrubs.

Authorities had been bracing for the possibility of catastrophic flooding because of heavy rain in the forecast for the first time in 10 months.

Evacuations were ordered beneath recently burned areas of Santa Barbara, Ventura and Los Angeles counties.

But only an estimated 10 to 15 percent of people in a mandatory evacuation area of Santa Barbara County heeded the warning, authorities said.

US Highway 101, the link connecting Ventura and Santa Barbara, looked like a muddy river and was expected to be closed for two days.

"All hell broke loose," said Peter Hartmann, a dentist who moonlights as a news photographer for the local website Noozhawk.

"Power lines were down, high-voltage power lines, the large aluminum poles to hold those were snapped in half.

Water was flowing out of water mains and sheared-off fire hydrants."

The first confirmed death was Roy Rohter, a former real estate broker who founded St. Augustine Academy in Ventura.

The Catholic school's headmaster, Michael Van Hecke, announced the death and said Mr Rohter's wife was injured by the mudslide.

Montecito is beneath the scar left by a wildfire that erupted on December 4 and became the largest ever recorded in California.

It spread over more than 1140 square kilometres and destroyed 1063 homes and other structures, continu to smoulder deep in the wilderness.