Marc Dodd, Wise County fire marshal, said the fire originated in the heating unit in the northeast corner of the store, which is a stockroom.
The store was open at the time and three employees were inside. They got out unharmed.
No one remembers turning on the unit, Dodd said, but there is a strong indication that it was turned on for the first time this season.
Dodd reminded residents that they should always have a heating unit checked out by a professional when starting it for the first time. And he also noted that it is a good idea to change out smoke detector batteries when the time change occurs, which is this weekend.
The fire started at 6:30 p.m. and quickly filled the downtown skies with thick smoke. Boyd units were assisted by Rhome, Newark and Decatur firemen in bringing the blaze under control.
The store lost a large amount of stock to heat and smoke damage, Dodd said.
