Crews at Grand Canyon National Park are working to suppress a 6,200-acre lightning-caused wildfire on the Great Thumb Mesa. It started last Thursday in pinion-juniper and brush, and fire activity yesterday was active in some areas with single-tree torching and 3-to-4-foot surface flames where the fire was consuming grass. Fire managers are working to protect sensitive natural and cultural resources. Smoke from the Thumb Fire is visible from both rims of the Grand Canyon and park officials are providing interagency support to the Havasupai Tribe and the Truxton Canon Agency.