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High winds returned to California's scorched wine country on Saturday, threatening advances firefighters made a day earlier against a series of wildfires that have killed more than three dozen people and incinerated thousands of homes.

The gusty conditions threatened a reversal of fortunes from Friday, when firefighters were able to carve wider barriers around some fires.

"Firefighters were able to make progress yesterday because the winds died down some," said Jaime Williams, a spokeswoman for the California Department of Forestry and Fire Protection, known as Cal Fire. "Today winds will be challenging."

Winds were expected to calm some on Sunday, she said.

All told, 16 fires have burned 214,000 acres — collectively the size of Dallas — across seven counties this week, forcing 100,000 people to evacuate their homes, with 40 people confirmed dead, according to Cal Fire and county authorities. Many more were still unaccounted for, including 223 people in Sonoma County as of Saturday.

"This is truly one of the greatest if not the greatest tragedy California has ever faced," Gov. Jerry Brown said. He added, "We're not out the woods yet. There are still fires burning, there's still danger."

Related: Northern California Wine Country Wildfires: Death Toll Rises

California authorities were investigating whether downed power lines and other utility equipment may have contributed to the cause of the fires, according to The Associated Press.

Sonoma County, where four simultaneous fires have caused more than half of the deaths since Sunday night, remained the epicenter of the destruction. Sonoma County, citing the coroner's office, said Saturday that the number of deaths there rose to 22.

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The kicked-up winds — measured at 21 mph with gusts up to 45 mph — pushed one of the fires toward the Oakmont neighborhood in Santa Rosa, according to Cal Fire. Officials have urged people there to flee the area, which includes a retirement community.

Smoke smolders from a fire-ravaged home destroyed by a wildfire on Oct. 14, 2017, in Sonoma, California. Marcio Jose Sanchez / AP

"Things went to hell last night," winemaker Dean Vincent Bordigioni told the AP. The owner of Annadel Estate Winery said he awoke at 3 a.m. with flames spreading across a ridge above his property.

Firefighters spent much of the week digging ditches around the fires to keep them from spreading. On the other side of the barriers are some of Santa Rosa's most expensive homes and a historic central plaza built centuries ago when the area was under Spanish rule.

High winds make it more likely the fires will jump those perimeters, officials said.

After losing ground overnight, firefighters were trying to keep the blaze from crossing into the city from the north on Saturday afternoon, with flames threatening streets on the outskirts of town, Steve Crawford, a Cal Fire operations chief, said.

Santa Rosa Police Chief Hank Schreeder said his department was fielding calls from people complaining about looting, and that, even with new evacuation orders for some parts of the city, officials were working on allowing residents to return to areas no longer under the threat of fire ─ and where the fire already destroyed homes.

That includes the area around Coffey Park, which was largely reduced to ashes.

Related: Wildfires Emitted a Year’s Worth of Car Pollution in Less Than a Week

"We're working on plans to open up areas hardest hit and give people the tools they need to rebuild their lives and start to move forward," Schreeder said in an update broadcast on Facebook.

While Sonoma County scrambles, eastern neighbor Napa County began to relax a little, as the fires did not appear to be spreading much there, officials said Saturday. There were no new evacuations, but authorities warned that the high winds and low humidity required continued vigilance.

"This morning I woke up and saw blue skies, but I can tell you I'm not the same person I was on Sunday," said Belia Ramos, a member of the county board of supervisors. "None of us are. That takes a toll on everybody."

Six people have been confirmed dead in Napa County, and there are 74 open missing persons cases, officials said. They warned residents returning to their homes not to clean up the debris because it probably contains toxic materials. Debris removal should be left to government crews, they said.

The Federal Emergency Management Agency has begun taking applications for individual assistance grants, but officials advised homeowners to seek compensation from their insurance companies first.

Amid the heartache, there was some good news for one Santa Rosa family. Jack Weaver, returning to the scene of his family’s destroyed home on Tuesday, found his parents' dog Izzy alive.

"When she came exploding out, that was an incredibly gratifying moment," Weaver, 37, said of the moment they found the 9-year-old Bernese mountain dog in a phone interview on Saturday.

Weaver’s parents, Clint, 68, and Kathy, 62, escaped the fire that destroyed their home on Monday. As they evacuated, Izzy bolted in another direction and was left behind.

"We didn’t believe she would’ve survived," Weaver said.