The massive 3-alarm fire at a warehouse in Crystal Lake on Monday was reportedly caused by a welding torch, the Crystal Lake Fire Rescue Chief said.

The Crystal Lake Fire Rescue Department was called at 2:54 p.m. Monday to Diesel Redemption, 6207 Commercial Road, for a structure fire.

Fire crews found heavy black smoke and fire showing from the building, which is a large one-story industrial warehouse. The Mutual Aid Box Alarm System (MABAS) was utilized and upgraded to the 3rd alarm, bringing firefighters and equipment from McHenry and Lake counties.

Crystal Lake Fire Rescue Chief Paul DeRaedt said that fire crews worked in a defensive mode, operating from the outside of the building by applying water through various hoses and three ladder trucks.

Photo provided to Lake and McHenry County Scanner by Rob Roderick.

A firewall in the center of the structure held the fire from spreading throughout the entire building, DeRaedt added. A roof collapse and partial wall collapse occurred in the area of the building where the fire started.

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The fire was deemed under control at 4:19 p.m. and crews remained at the scene extinguishing hot spots.

DeRaedt said that a 911 caller reported the business was working with a cutting torch before the building caught fire. Fire investigators and the Office of the State Fire Marshal are investigating.