In this photo provided by the U.S. Forest Service, a Hotshot fire crew member rests near a controlled burn operation at Horseshoe Meadows, as crews continue to fight the Rim Fire near Yosemite National Park in California Wednesday, Sept. 4, 2013.
Mike McMillan/AP
It's been four weeks since the Rim Fire began burning near Yosemite. So far, it's consumed nearly 400 square miles, making it the third largest fire in California history.
A hunter's illegal campfire allegedly started the blaze, but how did investigators figure that out?
For answers, we reached out to Paul Steensland, a retired fire investigations specialist who spent more than 20 years with the U.S. Forest Service.
