The size of the Silverado Fire, which was 50 percent contained Sunday night after burning for more than two days, has been revised downward to 968 acres, officials said. Authorities had earlier reported the burned area was 1,600 acres.
Six firefighters were injured while battling the blaze, which prompted mandatory evacuations that have since been lifted.
The fire was located in the mountains of Cleveland National Forest south of Corona, and broke out Friday morning.
Officials determined the blaze began in the backyard of a home in the 30000 block of Silverado Canyon Road, but the cause was under investigation.
Continuing improvement was expected, but officials stopped short of estimating when the fire would be fully contained.
"The juggernaut has started rolling down the hill, and we will get around this fire and put it out," Capt. Jim Wilkins with the U.S. Forest Service said.
About 1,428 officials battled the blaze Sunday.
Six firefighters were injured since the fire began, mostly due to heat-related injuries, Orange County Fire Authority Capt. Steve Concialdi said.
No homes or civilians were harmed as of Sunday evening.
Shortly after 7 p.m., authorities announced that mandatory evacuation orders had been lifted for the Silverado Canyon area.
Only residents would be allowed to access homes east of 30311 Silverado Canyon Road, according to a news release from OCFA and Sheriff's Department. The area remained closed to non-residents.
Those who live in the area should be prepared to show identification and proof of residency to law enforcement officials, the release said.
Officials urged motorists to drive slowly in the area due to hazardous road conditions and the presence of public safety equipment.
Officials were working to fix power outages that impacted 71 Southern California Edison customers after a power pole was burned.
Power was expected to be restored by Sunday night, officials said.
A high of 107 degrees was expected Sunday with 26 percent humidity and winds around 10 mph according to the National Weather Service.
Temperatures over 130 degrees in some canyons were felt Saturday, with the average temperature being 105 degrees, Wilkins said.
The heat was expected to wane beginning Monday with temperatures dropping to 104 degrees and reaching 92 degrees by Thursday.
Air quality in the area had improved since the blaze broke out Friday and was expected to continue getting better, Wilkins said.
KTLA's John A. Moreno contributed to this report.