A fire at the old NuTone facility appears to have started because of a welding torch, according to Cincinnati firefighters.

Firefighters were called to the building at Red Bank and Madison roads this week.

Heavy smoke was pouring from the three-story commercial building when crews arrived. A second crew was called in when firefighters realized the building was under demolition, fire officials said. Nearby residents were told to shut their doors and windows because there were chemicals inside the burning building.

Sixty firefighters worked to extinguish the blaze, Firefighters believe a welding torch may have caused a smoldering fire in the roof .

There were no injuries and it was unclear how much damage the fire caused. The fire remains under investigation.

The owner of the 29-acre site is RBM Development Co. It signed a development agreement with the city of Cincinnati in February and announced plans to build a new headquarters for Medpace Inc. on six acres.

The state of Ohio’s Clean Ohio Fund awarded a $2 million grant to RBM to demolish eight of the nine buildings on the site and rid it of any environmental contamination. The first stage of that, happening now, included asbestos removal and reclamation of usable materials from the buildings, said Kay Nolen, Medpace’s general counsel.

“My understanding is that the company that is tearing down some of the buildings observed some smoke and called the fire department. They were doing some work on the roof,” she said.

The contractor responsible for the demolition is O’Rourke Wrecking Co., Nolen said.