HILLSBORO, Ohio (AP) — An explosion at an auto repair shop in Ohio that killed three people and sent a fourth person to a hospital sparked a massive fire that burned for hours and spewed thick, black smoke into the air.

The Tuesday afternoon blast at Jimbo’s Auto Repair in Hillsboro was felt at several nearby sites, including the Paint Creek Joint EMS & Fire District, whose crews quickly responded to the scene. The heavy smoke was visible miles away.

Information about the three people who died was not immediately released by the Montgomery County Coroner’s Office. The injured person remained hospitalized Wednesday in stable condition.

The fire burned for several hours before it was extinguished around midnight. Firefighters had to contended with frigid conditions while battling the blaze, and Hillsboro city workers applied salt to nearby soaked roadways to prevent them from freezing over. Some roads in the area were also closed for several hours.

The cause of the explosion remained under investigation Wednesday. The State Fire Marshal’s Office is the leading the probe, and the U.S. Department of Labor’s Occupational Safety and Health Administration will also investigate.

Hillsboro is about 50 miles (80 kilometers) east of Cincinnati.