On Thursday, a Michigan State Police Fire Investigator visited the scene and ruled that the fire had been "incendiary" and deliberately set, constituting arson.
As a result, state and local police continue to investigate the incident, hoping to find those responsible.
"Evidence has been collected," said Reaves, "and along with (Michigan) State Police, the Imlay City Police Department is involved in finding the suspect(s)."
Anyone having information is asked to contact the county's anonymous Arson Tip Line at 800-441-7766 or call the Imlay City Police Dept. at 810-724-2345.
Reaves said firefighters from Imlay City and Attica Twp. fought the blaze for about four hours, but could not save the one-and-a-half-story structure.
"Due to the balloon construction (no fire stops in older-type buildings), the fire quickly went from the basement area to the roof," he said.
About 30 firefighters responded to the the scene, as did Imlay City police and Lapeer County EMS personnel, Reaves noted.
"Officer (Kevin) Homer's attention to detail on patrol helped gave the fire departments an edge over a fire that could have been much worse had it gotten bigger before being noticed," said Reaves. "The house next door was never in danger. That was a plus because firefighters didn't have to worry about radiant heat damaging other buildings."