The agency said there is no indication the hunter was involved with illegal marijuana cultivation, which a local fire chief had speculated as the possible cause of the blaze.
No arrests have been made, and the hunter's name was being withheld pending further investigation, according to the Forest Service.
A Forest Service statement gave no details on how the illegal fire escaped the hunter's control.
The Rim Fire began on Aug. 17 in an isolated area of the Stanislaus National Forest and has burned nearly 371 square miles — one of the largest wildfires in California history.
Officials said 111 structures, including 11 homes, have been destroyed. Thousands of firefighters were called in to battle the blaze, which at one point threatened more than 4,000 structures,
The blaze is now 80 percent contained.
