Crews were called to the Waldun Forest Products Mill in the 9000 block of 287th Street just after midnight.
Fire crews arrived to find the mill engulfed in flames.
Assistant fire Chief Mark Smitton says there were some difficulties in fighting the blaze.
"We had a lot of electrical sparks and the Hydro wires were sparking and creating problems for us on the initial attack."
No one was injured in the fire, but about 100 people are expected to be out of work.
The cause of the blaze has not been determined.
"We’re looking into all possibilities. During the day on Saturday they do do maintenance involving welding and that’s going to be one of the possibilities that we’re going to be looking into," Smitton said.
"We’ve still got quite a bit of investigation to do."
Mill owner Kirk Nagy was on scene Sunday afternoon.
"The emotions take over the logical facts. You just are overwhelmed with it," he said.
"It's hard. We're just coming into what should be the busiest time of year in the fall and we're not going to run next week, that's for sure."
Nagy says he'd like to rebuild the mill, but it's too soon to know whether it will be possible.
"We've got a dozen or 14 guys that have been here 30 years or more ... and I think just about everyone working on this ... so the money is one thing, but the more important thing is the people side."