EL DORADO NATIONAL FOREST (CBS SF/AP) — The Caldor Fire in the Sierra grew again overnight but the advance was not as explosive as it had been earlier in the week because of increased humidity, fire officials said Thursday.

The wildfire in the El Dorado National Forest burned over 65,000 acres by Thursday morning, according to Cal Fire and the U.S. Forest Service, which have unified command over wildfire operations. There was still zero containment since the fire began Saturday evening in the Cosumnes River Canyon area in El Dorado County.

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The cause of the fire was still under investigation Thursday.

A destroyed home during the Caldor Fire in Grizzly Flats, California, U.S., on Wednesday, Aug. 18, 2021. (Eric Thayer/Bloomberg via Getty Images

Fire officials said spotting and rollout continued to be the main contributor to fire spread throughout the evening. The spot fires started by flying embers often stay hidden for long durations because of the dense timber and limited road access.

The wildfire behavior was expected to increase during the day Thursday when the inversion layer lifts, fire officials said. Multiple spot fires were expected along the north and northeastern edge of the fire, even as a Red Flag Warning for the area ends at 11 a.m.

An emergency forest closure of all National Forest System lands, roads, and trails within the Eldorado National Forest has been in effect since Tuesday and will remain until September 30. The closure is designed to allow for evacuations, emergency response, and property access, while also limiting the public’s exposure to fire danger and impaired visibility due to smoke.

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CALDOR FIRE: Incident Information, Evacuations, Maps

Current mandatory evacuations include:

  • Grizzly Flat: The areas on Grizzly Flats Road east of Kendra Way into Grizzly Flats Proper. The areas of Diamond Railroad Grade, Old School House, Sweeney Road, Caldor Road, and Steely Ridge.
  • Grizzly Flats Road east of four corners in Somerset into Grizzly Flats Proper.
  • The areas of Myers Lane, Varmet Ridge Road, Rodwell Canyon Road, Snowbird Lane, and Mehwald Lane.
  • East of Sly Park Road between Highway 50 and Mormon Emigrant Trail to Ice House Road. This includes the communities of Pacific House and Fresh Pond.
  • North of Highway 50 ,east of Forebay Road to Ice House Road.
  • Intersection of Perry Creek and Hawk Haven , the East side of Fairplay Road from Perry Creek South to Cedarville Road. This includes Slug Gulch, Omo Ranch, and all roads off of Slug Gulch and Omo Ranch.
  • All roads off of Omo Ranch from Cedarville Road to Hwy 88.
  • The area between Highway 88 and Mormon Emigrant Trail
  • South of Highway 50 from Snows Road to Ice House Road.
  • Between Highway 50 and Slab Creek from Snows Road to Ice House Road.
  • South of Highway 50 from Ice House Road to Silver Fork Road. This includes the community of Kyburz.
  • North of Highway 50 from Ice House Road to Silver Fork Road to include Ice House Reservoir, Union Valley Reservoir, and Loon Lake.

New evacuation warnings were issued for parts of Amador County south of the fire perimeter. On Wednesday, the fire’s northern edge reached U.S. Highway 50 and prompted a mandatory evacuation of the community of Kyburz. Areas of Pollock Pines along Highway 50 have also been evacuated. Thousands in the area have been forced from their homes.

Dozens of homes have burned in the Grizzly Flats area and two people were hospitalized with serious injuries. The fast-changing nature of the fire has prevented crews from determining exactly how many structures have been lost.

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Close to 7,000 structures are currently threatened, Cal Fire said Thursday.