Officials with the Coronado National Forest said the Ventana Fire was reported around 3:30 Tuesday morning.
The fire is in the burn scar from the 2020 Bighorn Fire.
During the day helicopters dropping water and tankers dropping red fire retardant could be seen working the fire on the front side of the Catalina Mountains.
As of 3:00 pm, the Coronado National Forest reported the fire was 0% contained and had burned at least 50 acres.
Officials believe the fire was started by lightning that moved through the area around that time.