An investigation is underway into the cause of a fire that killed a Natchitoches Parish man. State Fire Marshal Butch Browning says Natchitoches firefighters found a single-story wood frame home on Highway 1226 in the Clarence community fully engulfed in flames when they got there. After the flames were out, they found a body in the living room -- a body they believe to be that of 73-year-old homeowner Cecil Fortner, who lived alone. The remains have been sent to the Natchitoches Parish Coroner's Office for autopsy. Investigators think the fire originated in the living room but they've yet to determine why. They haven't even been able to determine whether the home was equipped with smoke alarms.