(CNN) — Firefighters continued to battle the Kincade Fire in California as the state’s largest utility said a transmission line broke near the blaze’s origin point minutes before it ignited.

The fire in Sonoma County has scorched 21,900 acres and destroyed at least 49 buildings, according to the California Department of Forestry and Fire Protection, also known as Cal Fire. About 2,000 residents remained under evacuation orders and the fire was 5% contained, officials said Friday morning.

In an incident report filed with state regulators Thursday, Pacific Gas & Electric (PG&E) said that just before the fire started Wednesday night, one of PG&E’s high-voltage transmission lines went out.

Swipe through photos of the Kincade fire below.

PG&E intentionally had shut off power in the area Wednesday to prevent equipment from sparking wildfires during dangerous weather conditions. That transmission line was not supposed to be “de-energized” because it was not part of the public safety power shutoff, according to the company.

PG&E said it became aware of the outage at 9:20 p.m., and state fire officials said the blaze started around seven minutes later.

Bill Johnson, the utility’s CEO, said it’s too soon to tell what caused the fire or where it started. An investigation is underway.

“Cal Fire, the experts in this, will draw that ultimate conclusion,” he said at a news conference Thursday night. “We still, at this point, do not know exactly what happened. Something happened and it de-energized itself.”

Friday morning, the blaze remained one of nine active fires burning in the state, according to Cal Fire. Among the others was the Tick Fire north of Los Angeles, which had burned 3,950 acres and was 5% contained.

Thousands of people evacuated

The Kincade Fire prompted massive evacuations and destroyed 49 structures by Thursday, commercial and residential, fire officials said. Among the areas still under evacuation orders was all of Geyserville, north of San Francisco.

Firefighters are facing difficult conditions, Cal Fire spokesman Scott McLean told CNN affiliate KPIX.

“The wind is definitely pushing the fire,” he said Thursday. “The area has a lot of brush and indefensible terrain. It’s hard to fight … It’s dark right now so we don’t have any eyes in the sky …They (the firefighters) definitely have a fight on their hands.”

When PG&E intentionally cut power to about 179,000 customers, it was the second time this month the utility shut off power to hundreds of thousands of Californians.

In recent years, PG&E has been criticized for the role its equipment played in a series of catastrophic blazes, including last year’s deadly Camp Fire.

More shutoffs and blazes

Hundreds of miles away in Southern California, more than 31,000 customers were in the dark Thursday night as a result of intentional power cuts there. Utility company Southern California Edison said an additional 386,000 customers are under consideration for more shutoffs.

The Agua Dulce area, where the Tick Fire is burning, was part of the ongoing intentional power outages, said Lois Bruce of Southern California Edison.

Fire risks will continue into the weekend

Critical fire conditions will hit Southern California on Friday, with gusts of up to 70 mph expected, along with relative humidity in the single digits and temperatures in the upper 80s and 90s, CNN Meteorologist Haley Brink said. Red flag warnings are in place for more than 18 million people in California, which means soaring temperatures, low humidity and strong winds will increase fire dangers.

“Another round of very strong winds combined with dry fuels and critically low relative humidity values will be present in Northern California, throughout the Sacramento Valley beginning Saturday night into Sunday,” she said. “A fire weather watch has been issued for over 7 million people throughout from Redding down to Sacramento, including the surrounding regions.”

Kincade and Tick are among the largest of nine fires burning in the state Friday morning, according to Cal Fire. The other seven are either fully contained or have burned less than 145 acres.

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