The Rim fire continues to grow, burning at least 1,500 more acres Wednesday, pushing the total acreage consumed to 237,341, officials reported.
The fire burning in and around Yosemite National Park is the fourth-largest in state history. It remains about 80 percent contained, and officials say firefighters are making good progress against a wildfire that has burned for nearly three weeks.
"It's going really well," said Pamela Baltimore, public information officer with the U.S. Forest Service, which is in joint command of the fire effort with the state Department of Forestry and Fire Protection. "Most of the work right now is in the southeast and northeast areas."
Authorities lifted evacuation advisories in Tuolumne County, after the earlier cancellation of advisories in Mariposa County. Several roads and campgrounds remain closed, including Highway 120 into Yosemite National Park.
Several news organizations reported that Twain Harte Fire and Rescue Chief Todd McNeal said at a community meeting that it was "highly suspected" that an illegal marijuana growing operation had sparked the blaze.
On Wednesday, however, Jerry Snyder of the U.S. Forest Service said the steep and inaccessible canyon where the Rim fire started Aug. 17 in the Stanislaus National Forest doesn't have the sort of 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, adding that lightning isn't to blame.
It could take months for investigators to determine what ignited the fire that has consumed more than 370 square miles of Sierra Nevada forests.
"They'll be able to tell whether there was an illegal campfire in there," Snyder said.
Battling the blaze, the largest in the United States this year, has cost $60 million in state and federal funds, U.S. Forest Service spokesman Trevor Augustino said. Full containment is not expected until Sept. 20.
A total of 4,359 firefighters remained on the lines Tuesday, down from a high of more than 5,000. Baltimore attributed the drop in numbers to teams hitting 14-day limits, rather than a reduced need. A new strike team is taking over command of the fire as its predecessor is demobilized.