The 1 1/2 acre Boulder Fire on Mount Elden northeast of Flagstaff continued burning Monday without spreading.
The wildfire in Coconino County was reported Sunday at about 1:30 p.m. Smoke remains visible from Flagstaff.
Boulders seem to be containing it so far, but flames still burn in light brush and between fallen trees from the old Radio Fire from the 1970s.
The U.S. Forest Service said steep terrain is a concern.
About 16 fire personnel are on scene, including firefighters from the Mesa Hot Shots of the Tonto National Forest. Flagstaff City Fire Department High Angle Rescue is also working with the Forest Service in the event that someone is injured.
No homes or structures are currently threatened.
The cause of the fire is unknown at this time.
No other information was immediately available.
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