FLAGSTAFF, AZ (3TV/CBS 5/AP) -- The U.S. Forest Service announced Thursday the likely cause of the Museum Fire that burned through a mountain pass near Flagstaff in July.
Investigators determined the wildfire, which started on July 21, was likely caused by an excavator striking a rock during operations, according to the Forest Service.
The Forest Service said the spark created a heat source that laid dormant until warm, dry and windy conditions arrived and caused it to grow into a small fire which eventually spread.
It burned 1,961 acres and prompted the evacuation of about two dozen homes.
[READ MORE: Museum Fire]
The Forest Service said rock strikes are possible during operations in steep slope and at this time, the investigation has shown that the cause of the fire was not related to negligence and all proper inspections of the equipment were conducted.
It was declared fully contained Aug. 15, but dealing with its aftermath is expected to top $13 million.
“It’s unfortunate that the Museum Fire started as the result of ongoing restoration work designed to reduce the risk of uncharacteristic wildfire and improve forest health and resiliency—especially in the Flagstaff area where citizens joined together to invest resources to help fund the Flagstaff Watershed Protection Project,” said Coconino National Forest Supervisor Laura Jo West in a news release.
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The Forest Service said the investigation also determined that the last piece of equipment was used 14 hours prior to the first report of the fire, and the operator had completed a one-hour fire watch before leaving.
The investigation remains under investigation by the Forest Service.
The Associated Press contributed to this report