The 19-day-old Rim Fire that burned sections of Yosemite National Park and destroyed 370 square miles of forest was started by a hunter who allowed an illegal fire to escape, the U.S. Forest Service and local law enforcement said Thursday.
In a statement, the Forest Service and the Tuolumne County district attorney's office said they were withholding the hunter's name pending further investigation and that no arrests had yet been made.
The Rim Fire, which was 80% contained Thursday, began Aug. 17 on the Stanislaus National Forest near the area known as Jawbone Ridge, the statement said.
Crews do not expect the fire to be fully contained before Sept.20. The far-off date is because the portion of the fire burning in Yosemite National Park is headed toward granite outcroppings that will act as a natural firebreak but won't be classified as technical containment.
Letting geological formations help will allow firefighters to focus some efforts inside the fire's footprint. Snyder said they have begun to cut breaks and start backfires in an effort to save grazing land, wildlife habitat and historic buildings left over from early timber camps.
"We don't want the entire interior to be burned too," he said.
Officials said 111 structures, including 11 homes, have been destroyed. More than 4,300 firefighters are still battling the blaze.
The Forest Service also said that despite earlier speculation by a local fire chief, there was no evidence of an illegal marijuana operation near the spot where the fire began.
Jerry Snyder of the U.S. Forest Service said that the steep and inaccessible canyon where the Rim Fire started does not have a water source that growers look for when they set up remote gardens.
"The lead investigator says there's no evidence of any type of grow in the area where the fire started," Snyder said.
Contributing: Associated Press