(CNN)A raging wildfire that forced massive evacuations in Northern California scorched thousands of acres in hours — and is expected to keep growing.
The blaze had claimed 49 structures by Thursday afternoon, Cal Fire said. It was unclear how many of those lost were homes.
PG&E said in an incident report that a transmission line failed Wednesday about 9:20 p.m. local time.
The utility had a worker out Thursday morning inspecting the line when fire personnel pointed out an apparently broken jumper on a tower. The location on the report is near where the blaze began.
The transmission lines were still active because wind speeds of concern for those are higher than for distribution lines, the company said.
The fire started at 9:27 p.m. Wednesday and the cause is still under investigation, Cal Fire has said.
The latest blackouts will continue at least through Thursday in parts of 17 counties, including Sonoma’s wine country. Red flag warnings are in place for more than 25 million people in Northern and Southern California, which means soaring temperatures, low humidity and strong winds will increase fire dangers.
Winds are expected to die down in Northern California by the afternoon, CNN meteorologist Chad Myers said, but could pick back up on Sunday.
Another big wind event is forecast later Thursday for Southern California, Myers said, where gusts could reach up to 65 mph.
“One spark will take a fire a long way,” Myers warned.
Southern California Edison (SCE), another utility in that part of the state, shut off power to more than 15,000 customers in Kern, Los Angeles, Riverside, San Bernardino and Ventura counties.
Farther south, more than 320 customers in Descanso and Alpine lost power after San Diego Gas & Electric turned it off, citing “high winds and dangerous weather conditions.”
Blaze burned 5,000 acres in three hours
The Kincade Fire torched more than 5,000 acres within first three hours, Sonoma County Sheriff’s Sgt. Juan Valencia said. At that rate, a football field would be burned every three seconds, according to CNN meteorologist Brandon Miller.
The blaze started in the area of the Geysers geothermal plant in Geyserville. The company that operates the plant, Calpine, “de-energized” its local power line system before the fire started, Calpine vice president of external affairs Brett Kerr said in a statement to CNN.
As the fire burned, winds gusted up to 76 mph nearby, the National Weather Service said.
The sheriff urged residents to heed those evacuation orders, not only for their safety, but for firefighting efforts.
“It helps us to fight the fire,” he said, “rather than have to rescue someone from their home.”
Ash was “falling like snow,” early Thursday in the burn zone, fire data scientist Nicholas McCarthy tweeted, referring to the burned residue as “pyrometeors.”
In October 2017, the Tubbs Fire ravaged tens of thousands of acres in Sonoma County and killed nearly two dozen people. In Santa Rosa alone, a fire wiped out thousands of homes in the city roughly 50 miles northwest of San Francisco.
Old Water Fire threatens Southern California
Another fire in San Bernardino County in Southern California prompted mandatory evacuation orders for at least 80 homes, according to the San Bernardino National Forest Service.
The Old Water Fire broke out around 2 a.m. Thursday and spread to about 75 acres within a few hours, the forest service said.
Firefighters were making progress, the forest service said, and containment was at 30%.
Approximately 400 personnel were fighting the Old Water Fire, aided by 50 fire engines and a helicopter.