A post on the wildfire's incident website said the U.S. Forest Service and the Tuolumne County District Attorney's Office had determined the hunter allowed the fire "to escape."
The announcement put to rest earlier reports marijuana growers in the Stanislaus National Forest started the fire.
The fire, which began Aug. 17, was reported to be 80 percent contained Thursday.
The reduction in the size of the fire has allowed many firefighters to leave, the Los Angeles Times reported.
Almost 4,000 firefighters were battling the blaze Wednesday, compared to 5,100 at the peak of the fire, the U.S. Forest Service said.
Forest Service spokesman Jerry Snyder said Wednesday access to the area of the fire's origin for would difficult for growers and there was no evident source of water for the plants.
The fire has destroyed at least 111 buildings, including 11 residences. The firefighting operation has cost $72 million so far.