SUPERIOR, WI (KDAL) - Superior firefighters responded to a structure fire at Swanstrom Tools, 3300 James Day Drive, around 3:30 on Wednesday morning. Employees who were arriving for work found smoke coming from the building and alarms sounding. Damage was limited to one corner of the production floor of the structure where equipment and inventory was stored. Damage estimates are about 100 thousand dollars. There were no injuries and the cause of the fire is under investigation.