By 8:30 p.m., firefighters had estimated containment of the Cloud Fire at 50%.
The U.S. Forest Service/San Bernardino National Forest tweeted "The forward rate of spread has been stopped" and "Firefighters have hose around the fire."
Fire agencies assigned 150 personnel to battle the blaze.
The fire was first reported in the area of Waterman Canyon near Highway 18 just before 6 p.m.
Highway 18 was closed in both directions as firefighters battled the blaze.
No injuries or property damage were reported.