Part of the 15 Freeway in the Cajon Pass north of San Bernardino was closed Wednesday afternoon due to a fast-moving brush fire.
Three lanes were closed on the northbound side of the freeway in the Cajon Pass in the Devore area. Some lanes reopened Wednesday night as firefighters gained ground on the hillside fire.
The Bronco Fire erupted on a day of extreme heat in Southern California. Flames climbed north to a ridge line, where the fire appeared to be holding at about 20 acres, firefighters said.
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"Aggressive wildfire engagement has kept #BroncoFire under 100 acres and obtained 20% containment," the San Bernardino County Fire Department said in a tweet. "Crews will continue engagement throughout the night and heavy presence is expected tomorrow. Cause is under investigation."
Thick smoke could be seen in the mountain pass between the San Bernardino Mountains to the east and the San Gabriel Mountains to the west.
Details were not immediately available about how the fire started north of Matthews Ranch Road. No structures were threatened.