The fires have scorched more than 20,000 acres, destroyed dozens of homes and disrupted thousands of lives.
The larger blaze 30 miles northeast of Los Angeles destroyed 72 buildings, including 50 vacation cabins and a turn-of-the-century ranger station in the mountains above Azusa.
Investigators said Thursday they believe the Azusa fire, which was ignited Sunday, was started by people involved in the animal sacrifice ritual.
``The ... investigation team has concluded candles associated with a ritual involving the use of fire and animal sacrifices started the fire,'' officials with the U.S. Forest Service said in a statement. It was unclear if any arrests had been made and no further information was immediately available.
That blaze shut down two main electrical transmission lines, and California's power grid managers were watching a third closely. It was 15 percent contained late Wednesday and was expected to be fully surrounded by Tuesday.
Sections of state Highways 2 and 39 remained closed and were being used only by fire engines carrying reinforcements.
On the north end of Los Angeles County, west of Palmdale, a 4,470-acre blaze has destroyed five homes near Leona Valley. It was 40 percent contained Wednesday night.
The blaze started Tuesday and burned through scattered ranches and homes, some with private dirt roads too rugged for fire engines to maneuver. It threatened hundreds of animals, including cats, dogs, horses, llamas, bison and parrots.
Among those rescued were 50 miniature dachshunds, mostly puppies, grabbed by sheriff's deputies as flames closed in on a kennel.
``The deputies saw I wouldn't leave without them,'' said owner Connie Brown.