The fire last month in Soudan Underground Mine State Park, was probably caused by the sparkes produced by maintenence, the Star Tribune said.
The park manager, Jim Essig, told Duluth News Tribune that it is not likely the mine will be open this summer for tours, although visitors are welcome above ground.
The damage from the fire in the mine included "charred timbers and melted PVC pipes and electrical wiring," the Star Tribune said.
When the fire started, there were crew members in the lowest 600 feet of the mine shaft, according to Duluth News Tribune.
The Star Tribune reports that the cost of repairs and cleanup is still unknown, but experts will be finding out shortly.