The Carr Fire in Shasta County had burned an area of more than 80,000 acres by Saturday morning, with a containment of still just 5 percent. The magnitude of the blaze jumped from around 48,000 acres Friday night, according to the California Department of Forestry and Fire Protection.
Firefighters worked "aggressively" throughout the night to try to contain the flames, officials said, but the fire has been "active in all directions and has made significant runs." Gusty winds, high temperatures and dry vegetation still have the potential to spur fire growth.
The "mechanical failure of a vehicle" ignited the Carr Fire in Whiskeytown on Monday, officials said. The flames ripped through northwest Shasta County then spread southeast, sweeping across the Sacramento River late Thursday and roaring toward the city limits of Redding, which is home to 92,000.
The blaze has claimed the lives of a bulldozer operator and a city of Redding firefighter, according to officials from the California Department of Forestry and Fire Protection, the U.S. National Park Service and the Shasta County Sheriff's Office. At least three firefighters have sustained injuries.
A total of 3,410 personnel are working to contain the fire, along with 328 fire engines, 17 helicopters and 62 bulldozers.
Officials have ordered road closures and the evacuation of thousands of homes threatened by the Carr Fire. The California Highway Patrol is going door to door to assist, officials have told reporters.
At least 500 homes, businesses and other structures have been destroyed by the raging blaze, while 75 others have been damaged. Nearly 5,000 other structures remain threatened, officials said.
Scott McLean, a spokesman for the crews battling the Carr Fire, told reporters that winds reaching 60 mph were fanning the flames and creating fire tornadoes, or "firenadoes," that move erratically and are strong enough to overturn vehicles "like toys."
Local journalist Tamara Damante was co-anchoring live coverage of the Carr Fire when she and her colleagues were forced to evacuate ABC affiliate KRCR's station in Redding. Damante said the "quickness" and "volatility" of the blaze was unlike anything she had ever seen before.
"As this fire was just exploding, it's just been inching closer and closer and closer to the station to the point where there was a neighborhood up in flames just about a mile away from the station, just across from the Sacramento River," Damante said during an interview on "Good Morning America" early Friday. "I've never seen anything like it."
ABC News' Max Beller, Frank Elaridi, Courtney Han, Will Gretsky, Rex Sakamoto and Alex Stone contributed to this report.