The Pope Valley fire in Napa County had grown 500 acres to 3,800 acres as of Wednesday morning, according to Cal Fire, which had forced 180 mandatory evacuations, but so far had not injured anyone in the area known for wine making, ranching and farming.
Cal Fire told NBC Bay Area that the fire was still at Tuesday's containment level of 30 percent, and 380 structures remained threatened. Seven structures had so far been burned.
Cal Fire firefighters said it was the largest wildfire in the state in weeks. Gov. Jerry Brown said he secured a federal grant to reimburse 75 percent of the firefighting efforts from a FEMA Fire Management Assistance Grant.
"We still have a ways to go," Cal Fire Batallion Chief Scott McLean said Wednesday. "We've got some pretty volatile fuels."
Early in the morning, winds blew the vegetation fire northeast into Lake City, but firefighters were happy that the fire growth seemed to be slowing. NBC Bay Area's chopper flew overhead, and spotted some blazes and hot spots still on fire. A total of 1,000 firefighters were working the blaze.
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"I"m still in shock. It's surreal," said Tina Marchetti, one of the many evacuees who hadn't been to her home in nearly 24 hours. "We've been waiting a long time."
The fire was first reported on Tuesday just after noon at a home north of the Aetna Springs Winery, off Butts Canyon Road, northwest of Lake Berryessa. The area is east of Calistoga and has a population of just about 600 people.
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Vineyard manager Scott Brown told the Press Democrat that neighbors told him some young men accidentally started the blaze while cutting weeds using a tool with a metal blade. McLean said he was familiar with the allegation, but would not confirm the account to NBC Bay Area on Wednesday morning.
State fire spokeswoman State McCambridge said Wednesday that the fire is not affecting the lucrative Napa Valley vineyards. Pope Valley is about 20 miles north of Napa Valley.
Roxann Schaubhut, who lives in the area, didn't get to go home late Monday night and seemed to be taking the nearby fire in stride.
"I really don't think it will get to our house," she said. "We've taken a lot of precautions."
Smoke from the vegetation fire was visible on Tuesday from several counties -- including Sonoma, Marin and Contra Costa. The smoke was also visible from nearby wineries.
Residents of the Berryessa Estates subdivision in Pope Valley had been evacuated, Cal Fire said. Evacuations were also are in effect on Snell Valley Road to the Lake County line.
Two evacuation centers have been setup at at Polk Valley School and at Middletown High School.
For Cal Fire reports on developments related to the fire, click here.
NBC Bay Area's Jean Elle, The Associated Press and Bay City News contributed to this report.