Fire broke out just after 5:30 p.m. Monday at One Source Equipment Rentals on Detroit Avenue in Morton.
A passerby called in the fire while driving on I-155. Thick black smoke was seen coming from the structure.
Morton Fire Chief Joe Kelly said crews knocked the fire down quickly and no other buildings suffered any damage.
Firefighters remained on the scene for several hours.
The cause of the fire remains under investigation.
No injuries were reported.