YOSEMITE NATIONAL PARK — It could take months for investigators to determine what ignited the wildfire that has consumed more than 370 square miles of forest in and around Yosemite National Park, officials said.
The fire was 80 percent contained Wednesday. But crews don't expect full containment before Sept. 20 because the portion of the fire burning inside the 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. Jerry Snyder of the U.S. Forest Service 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.
Investigators have ruled out an illegal marijuana grow as a potential cause, ending speculation by a local fire chief that the gardens that plague federal land could be to blame.
The steep and inaccessible canyon where the Rim Fire started Aug. 17 in the Stanislaus National Forest doesn't have a water source that growers look for when they set up remote gardens, Snyder said.