Roaring wildfires in California wine country have prompted fresh evacuations as officials brace for the possibility of stronger winds feeding the flames of blazes that have already claimed at least 21 lives and left hundreds missing.

Across the state, firefighters were battling 22 large conflagrations that had spread across more than 170,000 acres, destroying more than 3,500 homes and businesses. The mounting death toll includes 11 people killed by one large fire, making it among the deadliest in state history. Dozens of toppled mobile phone towers around the state meaning communication are limited in many areas.

Blazes have already consumed large swaths of Sonoma, Napa and Mendocino counties, incinerating entire residential blocks and forcing from homes, hospitals and nursing facilities. Officials imposed a new set of mandatory evacuation orders overnight. Reports of missing persons continued to pour in, with Sonoma County Sheriff Rob Giordano saying officials had found about 110 of the roughly 670 people reported missing.

“The wind's going to pick up this afternoon. There's a lot of concerns with where the fire will go”, Mr Giordano said, adding that “this is still a very serious event” as he detailed “many more” evacuations conducted overnight and urged people to leave their homes proactively.

While annual wildfires are a fact of life in California, it is unusual for them to inflict such damage on urban centers. Sections of Santa Rosa have been utterly annihilated, brick chimneys rising from the twisted and blackened heaps of what were once houses.

Thousands of firefighters dispatched to battle the blazes have yet to make significant progress. As of Wednesday morning, the Tubbs Fire - which has destroyed more than 500 buildings and leveled parts of Santa Rosa - remained at zero percent containment. The Atlas Fire in Napa County was only three percent contained and had burned over 40,000 acres.

Mansions burn in California wildfires Show all 7 1 /7 Mansions burn in California wildfires Mansions burn in California wildfires The local fire department has deployed up to five helicopters and six aircraft to drop water on the fire Getty Images Mansions burn in California wildfires Local residents watch as homes are threatened by the fire MARK RALSTON/AFP/Getty Images Mansions burn in California wildfires A helicopter dumps water onto flames on the hillside as houses burn MARK RALSTON/AFP/Getty Images Mansions burn in California wildfires Local residents Steve Wells (L) and Scott Douglas (R) pack their cars after police issued a mandatory evacuation order MARK RALSTON/AFP/Getty Images Mansions burn in California wildfires Santa Barbara County Fire officials said around 2,000 people were ordered to evacuate AFP Mark Ralston Mansions burn in California wildfires The wind-driven wildfire destroyed homes and forced hundreds of residents to flee in the California coastal town MARK RALSTON/AFP/Getty Images Mansions burn in California wildfires A large smoke cloud shrouds the sky as residents evacuate during the Jesusita Fire MARK RALSTON/AFP/Getty Images

A separate fire in populous Orange County, the home of Disneyland, had destroyed 15 buildings but was at 45 percent containment

Firefighters and residents got a brief respite on Tuesday as the high winds that initially powered the fires dissipated. But officials on Wednesday were facing revived winds that could help fan flames and launch embers into new areas, expanding current fires and igniting new ones, with weather forecasts saying gusts could reach up to 50 miles per hour (80 kph).

“While these winds may hamper the efforts of firefighters, they will also increase the risk for new wildfires”, an alert from CalFire warned.

The return of powerful winds, whipping through a landscape that remains “critically dry” after California just emerged from five years of record drought, was fueling a “critical, catastrophic event”, California Department of Forestry and Fire Protection Ken Pimlott told reporters.

“We are literally looking at explosive vegetation”, Mr Pimlott said, noting that the fires were not subsiding at night.

“Were not out of the woods and we’re not going to be out of the woods for… a great number of days to come”, Mr Pimlott said.

For newly homeless residents of Santa Rosa, the largest city in Sonoma County, that news threatened to prolong an anxious limbo.

Even before officials mandated a new round of evacuations, shelters around the city were swelling with displaced people. Among them were residents of nursing home and two Santa Rosa hospitals.

At a public auditorium converted to a relief center, elderly evacuees were sprawled across cots in multiple rooms. Even as donations have poured in, a sign on door testified to continued needs: washcloths, walkers, pillows and reading glasses were among the items in demand.

“It’s been tough getting some of the equipment we need”, said Joan Acquistapace, a registered nurse who was volunteering to help oversee medical care for the evacuees, noting that she was short on glucometers. “We’re just waiting a little longer”.

Many people are still searching for loved ones who were forced to flee their homes in the middle of the night. At the evacuation center, columns of post-it notes stuck to an entrance door sought more information. “Molly, Elizabeth and Jason Want to Get You Home”, read one.

“They started wheeling us all out and we saw the ambulances and the buses”, said 92-year-old Ruth Hosty, who said in her rush to leave her retirement home she forgot to grab the address book with her daughter’s phone number. “I’m anxious to talk to her”.

Other residents were anxious to return to their homes, at least to grab personal effects they left behind in the scramble to leave and that remain imperiled by the flames.

“From now on, I’ll have my bags packed”, said 51-year-old Paul Puntous, who was among a crowd of residents being turned away by a sheriff’s official at the entrance to their still-evacuated neighborhood on Tuesday.

“We had no plan; now we’ll have a plan”, he said, adding that he wished he had taken items like gift certificates and passports.

But Mr Puntous had no time to weigh those options at 2am, when the sound of burning “pops and snaps” was followed by the blare of a sheriff’s loudspeaker ordering people out of their homes. A desperate race to safety followed in which he briefly considered abandoning his vehicle.