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Hundreds of buildings have been lost to a fast-moving Northern California wildfire that had forced thousands to flee Sunday and hospitalized four firefighters with second-degree burns.

The so-called Valley Fire in Lake County, northwest of Sacramento, erupted early Saturday afternoon and rapidly burned through brush and trees parched from several years of drought, according to the California Department of Forestry and Fire Protection, or CalFire.

The fire spread quickly, growing from 50 acres to 400 acres just before 4 p.m. (7 p.m. ET) Saturday, to 50,000 acres by Sunday afternoon. In a briefing at the Napa County fairgrounds, which has been turned into an evacuation center, officials said that the blaze was still at zero percent containment.

During the fire's first 24 hours, Napa County Fire Chief Barry Biermann said, authorities had one task in mind: "life saving."

Entire towns, as well as residents, along a 35-mile stretch of highway were ordered to flee their homes. "In some cases," Cal Fire spokesman Daniel Berlant said earlier Sunday, "residents only had minutes to evacuate."

Cal Fire spokesman Dave Shew said the fire had destroyed at least 400 mostly single-family homes. Some apartment buildings and at least 10 commercial structures were also burned, shew said.

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Lake County Sheriff's Office deputies were also trying to confirm reports of one person killed by the fire.

There is a report of a fatality on the #ValleyFire. That report is still being confirmed with the sheriff's office. — CAL FIRE PIO Berlant (@CALFIRE_PIO) September 14, 2015

Gov. Jerry Brown declared a state of emergency in Lake County on Sunday, less than 24 hours after the fire sparked, and CalFire called all personnel to report to duty, canceling any scheduled days off. One thousand firefighters were dedicated to battling the Valley blaze as of Sunday morning, and Berlant said more were on the way.

The four injured firefighters, who were members of a helicopter crew, were reported stable at UC Davis Medical Center, according to CalFire.

The fire destroyed homes and buildings as it burned through the town of Middletown, where authorities told NBC News that fire hydrants had run dry. Explosions could be heard all over town as propane tanks burst into flames, indicating that another building was being engulfed in flames.

This is what it sounds like when a 2000 gallon propane tank ignites. #ValleyFire pic.twitter.com/36XDKdwrvN — Gadi Schwartz (@GadiNBCLA) September 13, 2015

Cal Fire spokesman David Shew said the fire will rank as one of the worst he's seen in terms of devastation during his 28 years with the agency.

Meanwhile, more than 4,000 firefighters battled a blaze in Calaveras and Amador counties, about 70 miles southeast of Sacramento, which was spurred on by "unprecedented fire conditions" and steep terrain that had helped the flames spread.

The fire’s rapid growth slowed overnight Saturday, and it grew by only about 200 acres, but it was still burning more than 100 square miles near the tree-studded Sierra Nevada. The blaze, dubbed the Butte fire, which flared Wednesday, was 25 percent contained by Sunday afternoon.

The wildfire had destroyed 81 homes and 51 outbuildings and was threatening about 6,400 more, Cal Fire said. Mandatory evacuation orders were in place for several communities.

"I lost my business — it's all burned up — my shop, my house, 28 years of living," Joe Thomas, who lives near the community of Mountain Ranch, told The Associated Press. "I got to start all over. It's depressing."

Thomas, who runs a tractor dealership and repair business, said he and his wife grabbed papers, his work computer, photos and their four dogs. But they left a goat, five ducks, six rabbits and more than 30 chickens behind.

"I turned the pens open and turned them loose. I just couldn't gather them up," he said. "All we want to do is go home. It's miserable."

Brown declared a state of emergency in the two counties Friday, helping free up funding and resources to fire the fire. More than 4,000 firefighters are assigned to the blaze, according to Cal Fire.

Twelve wildfires are raging across California, prompting the National Weather Service issued air quality alerts for a large swath of the middle of the state. "If you live anywhere in Northern California, expect to see smoke," Berlant said.