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(Reuters) - Ten houses and 22 outbuildings have been destroyed in a wildfire that swept through parts of the Sierra Nevada mountains in California over the past week and continues to burn, a fire official said on Sunday.

No residents of the homes were hurt, said Tom Piranio, a spokesman for the California Department of Forestry and Fire Protection. Firefighters were only recently able to enter the burned areas to tally the structural damage caused by the King Fire, he added.

About 12,000 homes have been evacuated since the blaze began on Sept. 13, Piranio said.

The fire has scorched more that 80,000 acres (32,400 hectares) and remains only about 10 percent contained, he said. The destroyed homes were spread across the burned area and not concentrated in one place, Piranio said.

Scattered rain storms, cooler temperatures and increased humidity helped firefighters on Sunday, Piranio said.

The fire has ravaged the El Dorado National Forest, a popular destination for outdoor enthusiasts northeast of Sacramento.

Investigators have arrested Wayne Allen Huntsman, 37, on charges of arson, accusing him of starting the blaze.

Huntsman pleaded not guilty on Friday and was being held in lieu of $10 million bail. The criminal complaint lists previous convictions for assault with a deadly weapon, theft and receiving stolen property.