A brush fire burned late Friday morning off the 57 Freeway in the San Dimas area.
The 13-acre fire was near Covina Boulevard, just off the freeway on a hillside. Traffic was backing up in the area as smoke drifted across the freeway.
Firefighters declared a knockdown at about noon. There was an initial threat to people in the Riverwood community area, but no structures were damaged.
Fire crews are planning to remain at the scene throughout the night to monitor hot-spots.
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Details regarding a cause were not immediately available.