Smithfield firefighters responded to a structure fire at 206 N. 4th St. shortly before 9 a.m.

Fire Chief Patrick Harris said occupants inside the home noticed smoke and fire coming through a duct after turning on the gas heat. "There is really no structural damage," he said. "The damage is primarily to the heating and cooling system."

No one was injured. "They evacuated the house and turned off the unit," Harris said.