A fire on Mount Lemmon, possibly caused by lightning on Sunday evening, was at 200 acres Monday morning.
A monsoon storm Sunday came with significant lightning, and one strike may have started the fire near the old prison camp on the mountain, Coronado National Forest officials said in a press release.
The Prison fire was reported Sunday evening by the lookout atop Mount Lemmon at a time when radar recorded more than 600 lightning strikes across the Coronado National Forest, said the Associated Press.
By around 10 a.m., the blaze had grown to 200 acres, said an update on the Incident Information System website.
Two crews of firefighters with water tenders and an engine, along with a helicopter, were fighting the fire.
The prison camp area is closed for the summer, and there are no businesses or homes threatened.
The fire comes a couple of weeks after the 10th anniversary of the Aspen Fire, which burned 85,000 acres and destroyed dozens of businesses and homes at Summerhaven and in the same area.
Forest officials have asked the public to avoid the area.