The blaze destroyed three houses, damaged another and destroyed three mobile homes, a cabin, a garage and about a half-dozen vehicles, the U.S. Forest Service said in a statement Tuesday. Eleven outbuildings, a commercial building and several smaller structures have also been lost.
The wildfire started Monday between Palm Springs and Hemet, near the rural Riverside County community of Mountain Center and grew to more than 22 square miles as of Wednesday morning.
More than 2,200 firefighters and 25 aircraft had the blaze 10 percent contained.
It was mostly moving east toward the desert and away from small communities of homes, summer cabins and ranches in the San Jacinto mountains. But a shift in the wind could easily sweep it back toward homes, authorities said.
"It's a rapidly changing animal," Forest Service spokesman Lee Beyer said.
Most of the damage occurred late Monday and early Tuesday as the fire more than doubled in size, but it was not assessed until later in the day.
"Honestly, we thought that the structure destruction was greater than it is," Forest Service spokesman John Miller said.
Miller said officials were especially surprised that the Zen Mountain Center survived, and credited firefighters.
"We really thought it was gone," Miller told the Riverside Press-Enterprise. "The crews hung on and saved it."
About 50 homes were evacuated along with Camp Ronald McDonald, which hosts programs for children with cancer and their families.
The fire also led authorities to close a pair of state highways and the Pacific Crest Trail.
A public pool about 20 miles away in Indio was closed because of ash falling on the water.
The fire raged in thick brush and trees at an elevation of 5,000 to 7,500 feet, sending flames 100 feet high. Some of the area had not burned in 35 years and the vegetation was dried out, Beyer said.
"We only had 40 to 50 percent of normal precipitation" over the winter and no rain at all since early April, he said.