Delta and Montrose county officials suspect high winds flared up a smoldering brush pile, sparking a wildfire that forced the evacuation of about 20 homes.
Montrose County Undersheriff Dick Deines says the pile that had been burned three days ago.
He says the fire started in his county at around 11 a.m. Wednesday, which grew to 700 acres.
Winds quickly spread the fire into neighboring Delta County, prompting Sheriff Fred McKee to order the evacuations.
No injuries were reported.
Firefighters contained the fire a few hours after it started.
Parts of western Colorado were under a red flag warning, advising residents that high winds, dry vegetation, and low humidity provide perfect conditions for devastating wildfires.