Authorities said Thursday an escaped fire started by a hunter sparked the Rim Fire, which has burned nearly 250,000 acres, but no charges have yet been filed.
The announcement of a cause was intended to debunk widespread reports that the fire was linked to an illegal marijuana grow, said Jerry Snyder, Stanislaus National Forest spokesman.
He said releasing such information in the middle of an investigation is "very unusual" but that there was "pressure" to do so.
The U.S. Forest Service and Tuolumne County District Attorney's Office are conducting a joint investigation.
They determined a hunter, whose identity is known by authorities but has not been released, "allowed an illegal fire to escape."
The person has not been arrested, authorities said. No further information was provided.
The Rim Fire started on a hillside in a remote part of the steep Clavey River Canyon, about a mile east of the Clavey's confluence with the Tuolumne River. It was discovered about 3 p.m. Aug. 17 by firefighting aircraft flying by the area en route to another fire on Cottonwood Road.
Reaching about 40 acres that day, the fire exploded by Monday afternoon, jumping the Clavey and Tuolumne rivers and then Highway 120 near Groveland and Buck Meadows. Over three weeks, it's grown into the state's third largest wildfire in recorded history.
The fire has scorched 246,350 acres, including 66,000 in Yosemite National Park, and has also leveled a popular family camp, killed untold head of livestock, and burned more than 100 buildings - including 11 homes and dozens of outbuildings - plus stands of timber.
The cost of fighting the fire was $84.8 million as of this morning.
Tuolumne County District Attorney Mike Knowles said the DA's Office does not comment on active investigations, but offered some legal insight into what could happen next.
The hunter, he said, could be charged with crimes. For one, fires are forbidden in the forest this year because of the high wildfire danger. Too, he could be criminally liable for injuries suffered by six emergency personnel.
The hunter could face jail time and also be ordered to pay restitution for the cost of fighting the fire and damage done.
Restitution orders can't be dissolved by declaring bankruptcy, unlike civil claims from lawsuits, so would follow the hunter indefinitely.
Authorities declined to say where the hunter was from, what he or she was hunting or what weaponry was being used.
However, Aug. 17 was the opening day of hunting season for archers hunting deer, bears and many game birds.
There is not a comprehensive public list of hunting permits.
To get a hunting permit the first time, one has to take a hunting education class, which can vary in topics covered and length. An instructor may not cover outdoor skills like safe fire use, said Janice Mackey, a California Department of Fish and Game spokeswoman.