The fire in the Angeles National Forest surged to 1,000 acres Thursday and sent out big clouds of black smoke amid afternoon temperatures in the high 80s and winds gusting at more than 20 mph.
About 200 homes in the mountain community of Green Valley were evacuated, but the order was canceled about five hours later as temperatures and winds dipped and the fire largely laid down, the U.S. Forest Service said in a statement.
But there was still no containment of the blaze that had plenty of fuel to consume, and heat was expected to return Friday.
"The growth potential of this fire is great," said Forest Service spokeswoman Sherry Rollman. "It's burning medium to thick brush on steep slopes."
About 500 firefighters struggled to get near the fire that was hard to reach in steep terrain.
Water-dropping aircraft were grounded overnight but set to return after daylight.
Both Southern California Edison and the Los Angeles Department of Water and Power said the fire was threatening their facilities and they were monitoring the blaze for potential problems, though none had been reported.
The lines that were in danger were transmission lines not distribution lines, and major outages were unlikely, LADWP officials said.
The blaze broke out at about 3:30 p.m. Thursday just north of Powerhouse No. 1, a hydroelectric plant near the LA aqueduct that has been operating for nearly a century.
Seven hikers had been reported missing near the fire, but search teams learned that all had left the area safely on their own, sheriff's Lt. Steve Sylvies told the Los Angeles Times.
One structure has burned but it was not immediately clear what it was.