SANTA ROSA, Calif. — A cluster of devastating wildfires that has killed at least 17 people and destroyed more than 2,000 homes and businesses raged unchecked across the state's treasured wine country, decimating vineyards and forcing desperate residents to find shelter.

Tens of thousands of Californians fled their homes, many of them holing up in shelters that authorities said could be operating for several days. Power outages and cellphone disruptions added to the chaos amid the fast-spreading blazes, prompting hundreds of missing persons reports.

The fires, fueled by dry grasses and brush, heat and low humidity, were fanned by wind gusts reaching almost 80 mph. Conditions improved somewhat on Tuesday, and the National Weather Service ended its "red flag" fire warning in some areas.

But communities remain threatened and many people are dealing with catastrophe. Jack O'Callaghan, 66, was among those who lost his home on Highway 12 near the town of Glen Ellen.

"We left at 2:15 in the middle of the night on Monday. I sent my wife and family earlier. I stayed pretty close to the end . . . Now I come back to this. It's all gone," O'Callaghan said, standing in the rubble of what was his house.

"I did manage to find my safe, the coins in it were all kind of melted. I found the two guns I had in my nightstand. My .45 colt, it's destroyed. And my beautifully restored 1959 ford truck. I guess I should be grateful. I almost ordered a new radiator for it last week, but then I didn't."

Eleven people died in Sonoma County, according to the sheriff's office there. Two people died in Napa County, three in Mendocino County and one in Yuba County, Cal Fire officials reported.

Makeshift shelters are being set up to provide life-saving sanctuary for displaced residents. At the Sonoma-Marin Fairgrounds, sisters Jamuna and Yamuna Maharjan were among 300 evacuees who sought shelter there. The sisters said they are relieved to have a place to go.

“There are a lot of people going through more difficult situations,” Yamuna, 28, said. The Maharjans live in an apartment complex near a Hilton hotel that burned down.

Homes and other structures continued to burn late Tuesday in some neighborhoods, and most areas remained unsafe for residents to return, said Barry Biermann, deputy incident commander for the California Department of Forestry and Fire Protection (Cal Fire).

"It's understandable that when people don't see smoke, they want to go back in," he said. "But the fires are still out there."

Bierman also pleaded with residents not to send in drones to view their properties, saying that could thwart efforts to combat aerial efforts against the fires.

In the town of Oakmont, a fire was cresting the hill and working its way down towards a retirement living community of several dozens homes. Firefighters and emergency services personnel were going house to house trying to convince those who had refused to evacuate that the time had come.

Firefighters were turning back journalists who are trying to get closer to the fire, saying "it's going to be here soon. it's too dangerous. go back now."

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Southern California was not immune — Santa Ana winds spread the Canyon 2 Fire in Anaheim, Calif.,burning at least a dozen homes in Orange County. A thousand more homes were evacuated.

President Trump pledged his support.

"The federal government will stand with the people of California, and we will be there for you," Trump said at the White House. Vice President Mike Pence, in California for a series of fundraisers, also pledged federal support "as your courageous firefighters and first responders confront this widening challenge."

Cal Fire said the string of fires ignited Sunday and Monday, burning more than 115,000 acres and making Monday one of the most destructive wildfire days in California history. The most damaging is the Tubbs Fire, a 27,000-acre inferno responsible for most of the deaths and destruction.

More than 3,200 people had moved to dozens of Northern California shelters.

Napa County Sheriff John Robertson said the victims included Charles Rippey, 100, and his 98-year-old wife, Sara. Roberson said the couple were "unable to be evacuated" from their home.

More than 100 people have been injured in the blazes, and authorities say they expect the death, injury and damage tolls to rise. Many neighborhoods swallowed up by the flames have yet to be reached by firefighters or evacuated residents.

Volunteers stood outside the Sonoma-Marin Fairgrounds shelter, guiding vehicles in and out. A sign in yellow read, “No volunteers or donations. We are full. Thanks.”

They’d already received sheets, clothes, children’s books, teddy bears and towels. A volunteer carted around two dozen donated boxes of Little Caesar’s pizzas trying to get evacuees to eat while others looked through the mountains of donated items.

“We’re just trying to do what we can to make sure we’re OK," Marjan Barabian said. Barabian and husband Basim Mughannam had been there with other Petaluma residents, trying to make sure the evacuees were cared for.

Sally Parks, 72, an American Red Cross volunteer walked around the fairgrounds advising everyone to wear their mask. The thick smoke had already turned most of the sky brown and the smoke had blocked out the sunlight.

Parks was so far the only Red Cross staff on hand and was waiting for officials to turn the fairgrounds into an official Red Cross shelter. But with the multiple hurricanes that have hit the nation including Puerto Rico, volunteers are spread thin, Parks said.

But the volunteers at the fairgrounds, who may have never dealt with a crisis before, were filling in the gap.

“They’re not trained, but it doesn’t matter at this point,” she said. Any help would do.

Facebook said Tuesday that it would donate $1 million to local organizations in Northern and Southern California responding to the fires.

Since the fires started, the Silicon Valley company said Facebook users had activated its "Safety Check" feature for 14 separate wildfires in about 24 hours, including the Tubbs Fire in Sonoma County, The Canyon 2 Fire and The Atlas Fire in Napa and Solano Counties.

In addition, nearly 200 people have posted requests for help (food, transportation, shelter) and more than 3,000 have offered help. Facebook users have also created fundraisers on Facebook to help victims of the fire.

Local area nurses started a clinic out of the Beverly C. Wilson Hall, where they set up chairs and cots for any incoming patients.

Susan Craig, a registered nurse who’d retired three weeks ago, sat at the table taking in patients. It’d been a busy day, and when she could, she would try to sneak in a bite from her sandwich.

She assessed each person that walked into the room: Some were asking for help, some just wanted to help.

And so far it’d also been a successful day. “We haven’t had to send anyone to the emergency hospital,” she said.

With the help of multiple registered nurses, nurse practitioners and a physicians assistant, they were pretty well staffed and spent most of the day trying to hand out masks for safety, checked people’s blood pressure and handed out over-the-counter medication for those who needed it.

Wineries took a hit. Paradise Ridge Winery in Kenwood, 10 miles east of Santa Rosa, confirmed on Facebook that its facility was consumed by the flames.

"All the Byck family and Paradise Ridge team is safe," the winery said. "Our hearts go out to all who have lost their homes and businesses. We are strong and will rebuild."

Noah Lowry runs an outdoor sports store in Santa Rosa. Lowry, his wife and their 2-week-old baby were forced to flee the hard-charging flames.

“I can’t shake hearing people scream in terror as the flames barreled down on us,” Lowry said.

Some towns were without power, leaving tens of thousands of people on edge, waiting to learn if they, too, must flee the fires that ravaged the oak-and vine-dotted hills of the area north of San Francisco.

Kevin Kress, 43, was one of the lucky ones. He stood Tuesday pouring water on smoking embers of the portico to his stucco house on Highway 12 near Glen Ellen. "I've probably put out five small fires in the area around my house just in the time I've been here today," he said.

His family got out Sunday night, but he came back Tuesday to see whether their house had survived. "Amazingly it was still here. The portico was smoking so a friend that I knocked it down. But the house is OK."

Kress had pygmy goats, most of which survived the conflagration. "Some of them were burned but a surprising number made it through."

Contributing: Jessica Guynn; Amber Sandhu and Jenny Espino, Redding (Calif.) Record Searchlight; The Associated Press