Authorities have not confirmed the names of the dead. Children are among the victims, said Santa Barbara County fire spokesman Mike Eliason.
• Deadly storm: The 17 deaths were reported in Santa Barbara County, authorities said.
• More missing: Officials said 17 people were unaccounted for.
• Rescue operation: More than 500 first responders and 10 dogs continued to search for people in Santa Barbara County.
• Trapped residents evacuated: First responders used a helicopter to rescue some of 300 residents trapped by debris blocking their way out of Montecito's Romero Canyon area, Santa Barbara County Sheriff Bill Brown. Some residents wanted to stay in their homes, Brown said.
• Hundreds of calls: As the storm hit hard between 3 and 6 a.m. Tuesday, sheriff's office dispatchers handled more than 600 phone calls for assistance, Brown said.
: Dozens of people have been rescued in Santa Barbara County,
officials said. The US Coast Guard said it used helicopters Tuesday to collect people from rooftops, including a couple and their three children
• Injured: Twenty-eight people were hurt in Santa Barbara County, officials said.
• Destruction: Floodwaters and mudslides destroyed 100 homes and damaged another 300 residences in Santa Barbara County.
• Road closed: US 101 in parts of Montecito and Santa Barbara will remain closed for at least 48 hours because of the muddy debris covering it, authorities said Tuesday.
'I just want to find my friend'
In Montecito, east of Santa Barbara, home after home is damaged or encircled by mounds of mud, furniture and fallen trees.
Diane Brewer has hopes of finding her missing friend Josie Gower, 69. Gower was at home with her boyfriend early Tuesday when a mudslide swept through the neighborhood.
"For some reason, she opened the front door" and was swept away, Brewer said.
The boyfriend also was carried away and became stuck between boulders before being rescued, Brewer said.
Brewer and others planned to search the property.
"I just want to find my friend," Brewer said, in tears.
Hours later, Brewer confirmed Gower's death.
"Josie grew up right around the corner from me; she was 15, I was 5," Brewer said.
She added: "It was always a full a life with Josie. Now, it's just a hole."
Family members waited for word about their missing loved ones. Many turned to social media in their search.
James and Alice Mitchell, an elderly couple from Montecito, are among those missing, the couple's granddaughter, Sarah Weimer, told CNN Wednesday. Weimer said her mother was in Montecito helping with the search.
Rebecca Riskin, the founding partner of Riskin Partners, a Montecito real estate company, is also missing, a relative, Lynne Creighton said.
Riskin began selling real estate in Los Angeles. In 1990, she moved to Montecito, where she climbed to the top of real estate industry, according to the biography on her firm's website.
'River of mud'
Thomas Tighe was outside his Montecito home when he heard "a deep rumbling, an ominous sound I knew was ... boulders moving as the mud was rising," he told CNN affiliate KCAL.
He saw two cars moving sideways down the middle of the street "in a river of mud."
Peter Hartmann said the destruction was everywhere.
"There were gas mains that had popped, where you could hear the hissing," he told the TV station.
"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."
Before the storm hit, Santa Barbara
issued mandatory evacuations for 7,000 people
, including in parts of Carpinteria, Montecito and Goleta, which are below areas scorched by wildfires, county spokeswoman Gina DePinto said.
"While some residents cooperated with the evacuations, many did not. Many chose to stay in place," said Brown, the sheriff.
Sheriff deputies spent Monday conducting door-to-door evacuations for 7,000 people in a mandatory evacuation area.
But the area where homes were destroyed, south of Highway 192, was not in a mandatory evacuation zone.
Rescue personnel still have areas to search, Brown said.
"It was literally a carpet of mud and debris everywhere, with huge boulders, rocks, (downed) trees, power lines, wrecked cars -- lots of obstacles and challenges for rescue personnel to get to homes," Brown said.
Oprah: Debris is 'everywhere'
Oprah Winfrey posted a video on social media of her trudging through the mud in the yard of her Montecito home.
"There used to a fence right here,"she said, pointing in the direction of a neighbor's home. "My neighbor's house, devastated." Winfrey said debris is "everywhere."
She said her home had minor damage, but it pales in comparison to what her her neighbors suffered.
The debris also shut down parts of the oceanside US 101, a major thoroughfare connecting Northern and Southern California.
A stew of floodwater, mud, tree limbs and other debris covered the highway in Montecito, making it impassable. Some cars were left on the highway, mired wheel-deep in the muck.
As workers clear debris to make areas accessible, more damage is revealed. Along Montecito's Coast Village Road, the mudslide overturned trees and covered the pavement. At one spot, a car appeared to be sheared in half -- its front half pointed skyward, jammed against a pile of muddy wreckage.
More than 1 inch of rain per hour
The rain fell at more than 1.5 inches per hour at one point early Tuesday in parts of Southern California. About a half inch per hour is enough to start mudslides, said Robbie Monroe of the National Weather Service in Oxnard.
The downpour fell in areas charred by recent wildfires, which burned vegetation that otherwise could make the terrain more resistant to mudslides.
The Thomas Fire
-- the largest wildfire in California's recorded history -- has burned more than 281,000 acres in Santa Barbara and Ventura counties since it began in early December. It was 92% contained, and officials don't expect full containment until later this month.
Montecito and Carpinteria are especially vulnerable to mudslides because the steep terrain in some places goes from thousands of feet above sea level to sea level in "a matter of just a few miles," said Tom Fayram, a deputy public works director with Santa Barbara County.
Mudslides are not uncommon to the area and can be deadly. In January 2005
, a landslide struck La Conchita in Ventura County, killing 10 people.