ANGELES NATIONAL FOREST (CBSLA.com) — Crews continued to battle a fast-spreading brush fire Saturday in the Angeles National Forest.

The fire reportedly grew to 2,500 acres by Saturday morning but that figure was later downgraded to 1448 acres by officials.

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The fire burned three cabins and an out building. Five firefighters have suffered minor injuries.

The blaze was 20 percent contained by Saturday evening, officials said.

Temperatures that soared near triple-digits did not help firefighters in their efforts.

Los Angeles County Fire and Angeles National Forest crews arrived on the scene at Highway 39 near Rincon Red Box Road shortly after 1 p.m. Friday. The fire spread quickly across the dry hillsides under triple-digit heat. By 2:45 the fire had jumped Highway 39 and was continuing to spread up a hillside as a vast smoke plume rose thousands of feet above the fire into the air.

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About 400 firefighting personnel responded to the scene. One helicopter involved in the firefight made an emergency landing alongside a reservoir, possibly after clipping some power lines in the area.

On Saturday, firefighting helicopters were patrolling the perimeter of the fire, looking out for flareups and hot-spots.

Highway 39 remained closed above East Fork Road on Saturday.

Mandatory evacuations remain in effect for campgrounds up and down the route.

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Investigators have not determined the cause of the fire.