A 15-year-old boy was being held Sunday in connection with a 500-acre wildfire that destroyed at least one home and threatened 30 others, forcing residents to evacuate.

Another boy, also 15, was released to his family after he was questioned by authorities, said Lt. Kevin House of the El Dorado County Sheriff's Department.

At least one of the boys was playing with matches when the fire started Saturday afternoon amid the heavily forested canyons between the cities of El Dorado Hills and Rescue, House said. He did not release their names.

The fire was 30 percent contained Sunday morning, and firefighters were struggling to protect the homes in its path, said Kathy Pennington, a spokeswoman for the California Department of Forestry. She was unsure how many people had been evacuated.

The blaze crackled through trees about 40 miles east of Sacramento, an area that has been extremely dry this summer. Temperatures Saturday neared 100 degrees.

Across the West, the National Interagency Fire Center reported 17 large active fires, including Oregon's Biscuit fire, which had burned about a half-million acres and was expected to be contained early next week.