The fire started Wednesday morning at the north end of the former Sappi Fine Paper plant. No injuries were reported.
Owner Doug Melching bought the plant last year and is demolishing the buildings to recycle materials. Melching said some employees were using cutting torches about four or five stories off the ground in the roof area on Wednesday. Sparks from the torches ignited a fire in some exposed wood.
Melching hopes to redevelop the site it as an industrial park.