As firefighters battle a wildfire in Northern California's famed Napa Valley wine region, officials are also investigating reports of illegal backfires in the area.

Cal Fire said as of Tuesday morning the Glass Fire that's burning in Napa and Sonoma counties had scorched some 66,840 acres and is now 50% contained.

“We have turned the corner on the fire as a whole,” Cal Fire division chief Ben Nicholls said during a briefing in Sonoma County.

CALIFORNIA WILDFIRE DESTROYS OVER 550 HOMES AS FIRE CREWS INCREASE CONTAINMENT, 'TURNED THE CORNER'

Over the weekend, Cal Fire that it was investigating reports of private citizens lighting backfires of their own to keep property from being burned up in the Glass Fire.

A firefighter runs past flames while battling the Glass Fire in a Calistoga, Calif., vineyard Thursday, Oct. 1, 2020.

A firefighter runs past flames while battling the Glass Fire in a Calistoga, Calif., vineyard Thursday, Oct. 1, 2020. (AP Photo/Noah Berger)

The agency told KTVU it could not confirm whether the reports were coming from Napa or Sonoma County.

But Cal Fire spokesman Scott McLean told the Santa Rosa Press Democrat the blazes were serious because hot, dry conditions mean such fires could quickly get out of control.

A firefighter walks a path as the Glass Fire burns along Highway 29 in Calistoga, Calif., on Thursday, Oct. 1, 2020.

A firefighter walks a path as the Glass Fire burns along Highway 29 in Calistoga, Calif., on Thursday, Oct. 1, 2020. (AP Photo/Noah Berger)

“You just don’t arbitrarily put fire on the ground without notification. There’s so much danger to that,” McClean told the paper. “There’s always reaction to that action, that’s how serious it is.”

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Backfires can be effective but risky, with officials saying they should only be conducted by those who are properly trained with sufficient resources.

Over 2,700 fire personnel are involved in the battle against the blaze, with some 408 fire engines deployed in the fight against the two-county blaze, according to the agency.

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The blaze started on Sept. 27 in the early-morning hours. A cause has not yet been determined.

The blaze has destroyed some 553 homes, with 297 in Sonoma County and 256 in Napa County have been lost so far. The wildfire is still threatening over 21,000 structures, according to fire officials.

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Dry conditions continue for the western U.S. on Tuesday, which is not helping the wildfire danger across the region.Private citizens are reportedly  lighting their own fires to keep their property from burning up

The current number of large wildfires burning across the U.S. as of Oct. 6, 2020.

The current number of large wildfires burning across the U.S. as of Oct. 6, 2020. (Fox News)

Air quality alerts are still in effect for parts of California, Oregon, and Colorado due to the smoke spreading from the current wildfires burning.

Fox News' Janice Dean contributed to this report.