Near Nucla firefighters are working to contain a lightning-sparked fire burning about 900 acres.
The fire began Saturday afternoon and was burning in pinon, juniper and oak.
Fire officials say they have no estimated time of containment.
Three seasonal cabins are threatened by the blaze.
Two bulldozers, three engines and 14 smokejumpers are among crews working to suppress the fire and build containment lines to protect the cabins and other property.
The fire is being allowed to burn in other areas where it could benefit wildlife habitat and vegetation.