The West Fork fire complex, which consists of the West Fork fire, the Papoose fire and the Windy Pass fire burning in the San Juan and Rio Grande National Forests, has been difficult for firefighters to tackle because of the mountainous terrain and up to 40 mph winds feeding the flames, The Denver Post reported Sunday.
Mineral County Commissioner Scott Lamb said the area also has a large number of beetle-killed spruce trees that "made it just inevitable that something would set it afire."
"This is probably far from over, if the weather doesn't change," Lamb said. "Wind is the most important factor in firefighters' ability to contain the fire."
The fires have prompted the evacuation of at least 1,000 people from South Fork. "Right now," said Mayor Kenneth Brooke, "everything is safe."
InciWeb.org said the West Fork complex was sparked by lightning on June 5 and is currently zero percent contained.
There were no reports of injuries.