The fire erupted at a building at Illinois 120 and Genessee Street, according to a Waukegan Fire Department battalion chief.
The building engulfed in flames is a former Salvation Army warehouse. The smoke could be seen from Chopper 7 HD miles away in the southwest suburbs near Interstate 55.
Several suburban fire departments assisted with the fire, including North Chicago.
There were no injuries. A portion of the roof collapsed.
A passerby likely called to report the fire about 6:10 a.m. at 133 S. Genesee St., which is a large one-story, commercial building with 12-foot ceilings and brick on the outside, said Waukegan Fire Battalion Chief John Schmidt. The building is vacant.
The Salvation Army moved out of that warehouse about 25 years ago.
Firefighters spent the morning putting out hotspots.
Schmidt said he does not know what could have started the blaze. "They are investigating that now and probably talking to the person who called it in,'' he said. "Fire prevention is out there now.''
The battalion chief said he doesn't remember any recent similar incidents there. It is located about two blocks west of the shores of Lake Michigan.
The Sun-Times Media Wire contributed to this report.