The Catalina Highway to Mt. Lemmon was closed to all non-residents Sunday afternoon after a fire broke out near mile marker 5.
The Coronado National Forest reported that the fire had burned between 150 and 200 acres.
The fire, which is called the Molino 2 wildfire, began in the Molino Basin Shooting Area and was climbing up the ridgeline to the north and the south.
The Pima County Sheriff's Department reported Sunday evening that no evacuations had been ordered.