Investigators believe a hunter sparked the monster wildfire which spread into America’s world-renowned Yosemite National Park and became California’s fourth biggest blaze ever.
They dismissed earlier reports that the so-called Rim Fire, which is now 80 per cent contained, was caused by activity on an illegal marijuana farm near the US landmark park.
“Investigators from the US Forest Service Law Enforcement and Investigations and Tuolumne County District Attorney’s Office have determined the Rim Fire began when a hunter allowed an illegal fire to escape,” said a statement by the US Forest Service.
“There is no indication the hunter was involved with illegal marijuana cultivation on public lands and no marijuana cultivation sites were located near the origin of the fire. No arrests have been made at this time.”
The hunter’s name is being withheld pending further investigation, the statement added.
The fire, which began on the afternoon of August 17 in the Stanislaus National Forest just outside Yosemite, now covers 95,442 hectares, according to the latest update on the Inciweb inter-agency website.
More than 4,300 firefighters are still working to contain the blaze, while aircraft have dropped more than 15.14 million litres of water and fire retardant over the last 17 days.
It is the fourth largest California wildfire since records began 1932, with an area five times that of Washington DC.
The largest in California history remains the 2003 Cedar fire in San Diego County, which destroyed 2,820 buildings and left 14 people dead after ripping through 110,000 hectares of land.
Authorities in California have in recent years faced increasing problems with marijuana farms hidden deep in the region’s rugged wilderness.
A 2009 fire that burned 36,420 hectares in the Los Padres National Forest near Santa Barbara was triggered by a campfire at a marijuana farm.