The Sierra Fire is burning in the Cajon Pass near the busy 15 Freeway at the base of the mountains.
The fire broke out around 4 p.m. Tuesday. It has burned about 200 acres and threatened some 30 rural homes. The blaze was 80 percent contained Wednesday night. Full containment was expected by Thursday evening.
Helicopters made massive water drops on the area overnight and reduced much of the blaze to white smoke.
Voluntary evacuations are in effect for residents along Glen Helen Road west of the 15 Freeway.
An evacuation center was established for residents at the Jesse Turner Center located at 15556 Summit Avenue in Fontana. Authorities were asking residents to take their small animals to the Devore Animal Shelter located at 19777 Shelter Way in San Bernardino.