From the transcript

They knew that it was a power line issue. They went out right away to take a look, and by the time they got from the station to their vehicles, the fire was called in. By the time they got to the fire, it was 15 acres and going through to 20. One of the things that we've been watching here, even though it's been hot and dry in Delta and Tok and Delta for most of the summer, we hadn't had wind. And this was the component that threw us into here with the wind that came on now.