The fire last month at the Soudan Underground Mine State Park near Tower was most likely caused by sparks produced by maintenance work in the shaft, according to the state fire marshal.
Workers were in the elevator shaft on March 17, replacing some of the steel sheathing that lines the lower levels of the shaft. The fire marshal's report said sparks evidently caused small pieces of wood to smolder and then burn.
Park Manager Jim Essig said it'll be a challenge to repair the fire damage, because the elevator that carries workers and supplies is very small, and can't handle big equipment.
"Any time you're working in that kind of constraints, it takes a few days to get a feel for what you're doing and make sure you're doing it in a safe way," Essig said. "It's going to be a little experimental as you start doing it, and then as you do it for awhile you start to find efficiencies on how to do the job quicker."
Essig said repair work will include replacing more steel sheathing, some of which is now damaged by the fire.
"We're still up in air exactly what to replace it with: Do we want to go back to steel sheathing or do we want to go to more of a concrete form like you see in the upper levels?"
The Department of Natural Resources said it's unlikely underground tours will resume this summer, but the park remains open for surface tours. And the DNR's web page has a virtual tour of the mine.