Firefighters were battling a vegetation fire that began Sunday afternoon in Fontana.
The fire was reported just after 2 p.m. along Sierra Avenue with winds pushing the flames southeast toward Riverside.
Homes in the area were threatened but no evacuations were issued.
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No structures were damaged and Sierra Avenue re-opened by 10 p.m.
A smoke advisory was issued in parts of San Bernardino County and Riverside County due to the fire affecting air quality.