U.S. Forest Service Spokesman John Miller said the blaze began at about 12:30 p.m.
The fire had grown to 1,100 acres by 11:30 p.m. Wind was a major factor in the speed and size of the fire.
The fire has been named the "Hill Fire."
The fire was 20 percent contained at 11:30 p.m. Winds had died down. Two homes have been damaged, and two other unknown structures have been destroyed.
Flames were threatening homes in the Oak Hills community, prompting mandatory evacuations.
The mandatory evacuation area has been reduced to south of Mesquite Street, east of Baldy Mesa Avenue, and west of Oak Hills Road.
Earlier mandatory evacuations ordered included the area west of Caliente Road, east of Baldy Mesa Road, south of Joshua Street, to the top of the Cajon Pass in Oak Hills and Jenny Street between Columbine Road and Braceo Street in Hesperia, but those areas were reassessed by 10 p.m. Friday.
A Red Cross evacuation center has been set up at the San Bernardino County Fairgrounds, 14800 Seventh St., Victorville, 92395. Large animals may also be taken to the San Bernardino County Fairgrounds.
Residents in need of assistance evacuating animals can call San Bernardino County Animal Control (800) 472-5609.
Area residents can contact the United States Forest Service Public Information Line (909) 383-5688.
I-15 is open in both directions but closures may occur periodically due to smoke.
Authorities say a firefighter was injured, but the extent of the injuries was unknown. He was airlifted to Loma Linda University Medical Center in unknown condition.
Some drivers were overcome by smoke inhalation while driving through the smoke. They were taken to a local hospital for evaluation.
Interstate 15 is a major route between Los Angeles and Las Vegas.
The next abc7.com update will be posted early Saturday morning.