BIG BEAR LAKE (CBSLA.com) — Fire crews on Sunday afternoon responded to a brush fire near Snow Summit Ski Resort in the San Bernardino Mountains.

The fire — burning just south of Big Bear Lake — was first reported at about 12:25 p.m. The fire grew to 10 acres by 1:45 p.m. and then 20 to 25 acres by 2:30 p.m. It had grown to 40 to 50 acres shortly after 3 p.m. The fire was spreading at a moderate rate of speed, the National Forest Service said.

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The charred area is near Knickerbocker Road and Pine Knot Avenue.

Mandatory Evacuations are in place for the area from Knickerbocker Road east to Georgia Road and south of Pennsylvania Road to the forest boundary, officials said.

Voluntary evacuations are in place for the area south of Brownie Lane, east of Thrush Drive, north of Switzerland Drive, and west of Summit Blvd.

An evacuation center has been set up at the Big Bear Convention Center located at the intersection of Big Bear Blvd and Division Road.

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Fire crews were on the scene Sunday afternoon into the evening and firefighting aircraft were dropping water and flame retardant on the blaze.

By 6:50 p.m., the fire was reported to be about 100 acres with 30 percent containment, authorities said.

Officials said the fire had moderate to heavy fuels and was burning brush and timber. Fighting the blaze was 300 personnel, 12 engines, two crews, four air tankers, two water tenders and 4 helicopters.

Forest Roads 2N06 (Radford), 1N54 (Clarks Grade), 2N93 (Wildhorse), and 2N10 (Skyline) are closed, as of 7:25 p.m. Sunday.

The cause of the fire remains under investigation.

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Officials said all schools in the Bear Valley Unified School District will be closed Monday with the exception of Fallsvale School in Forest Falls.