It happened a little after 5am on Baird Creek Parkway, just off Humboldt Road.
The Green Bay Metro Fire Department is treating the fire as suspicious until they can figure out the cause.
"Had it not been so wet out lately, this fire could have easily spread to the grass and we could have had ourselves a little bit of a fire in the creek," Assistant Chief Mike Nieft said. "But it's been wet and it was a steel building, which kept all of the heat and basically all the sparks and everything contained inside the structure itself. So we got kind of lucky."
The owners of the property, living in Texas, have been notified.
This is the fourth fire under investigation by the Fire Marshall's office and Arson Investigation Task Force since Saturday.
Copyright Copyright 2014 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.