A fire agency earlier reported the fire had scorched 2,500 acres, but the U.S. Forest Service revised that number to 1,804.
About 800 firefighters were on scene. Two injuries were reported. One firefighter was struck by a rock Thursday. Another firefighter was treated for heat exhaustion Friday afternoon.
Firefighters struggled with the steep and rugged terrain, and shifting winds made it hard to predict the direction of the wildfire.
Seven helicopters and seven fixed-wing air tankers were deployed in the firefighting effort.
Even though it is hot, dry and windy, Nathan Judy, a spokesperson for the U.S. Forest Service, said the weather is helping keep flames away from homes in Green Valley.
"This wind is pushing toward the south, which is good for us," he said. "If we had a wind shift, pushed back toward the north northwest, it would again threaten Green Valley, the community there, and we would have to reestablish those evacuations that we had last night."
The Powerhouse Fire broke out around 3:30 p.m. Thursday north of Santa Clarita, along San Francisquito Canyon Road. Firefighters called the blaze ferocious and relentless.
"The fire behavior for this time of the year is off the charts," said Capt. Mike Coggins of the L.A. County Fire Department.
Evacuation orders affected as many as 300 homes in Green Valley. Many left, but Paula Thomason did not.
"We could see the flames just coming over all the hills, and it was jumping," Thomason said.
From her porch, she watched air tankers dump hundreds of gallons of water on hot spots. Residents were later allowed to return.
Some roads remain closed as the firefight continues. Only residents and emergency personnel are allowed to enter San Francisquito Canyon Road from Copper Hill, and only emergency personnel can enter the areas between Calle Daggett and the Department of Water and Power Village on the San Francisquito Canyon Road.
On Friday afternoon, Camp Mendenhall Probation Camp and areas north of South Portal Road and west of San Francisquito Canyon were evacuated due to the fire.
Officials say the estimated date of full containment is Wednesday, June 5. The cause of the fire remains under investigation.
County health officials warned that air quality in the Santa Clarita Valley and San Gabriel Valley mountains will be unhealthy for sensitive individuals throughout the weekend due to the fire, and they urged residents to take precautions and avoid unnecessary outdoor activities.
City News Service contributed to this report.