Watertown Fire Rescue has completed the fire investigation for the fire that happened on 8/31/15 at SD Livestock Sales 925 10th St NW Watertown SD 57201. The cause of the fire is ruled Undetermined, the probable area of ignition was in the area of the Utility room. The (ATF) Ammo Tobacco and Firearms, (DCI) South Dakota Criminal Investigation, South Dakota Fire Marshal’s Office and Watertown Police Department assisted in the investigation. It is common practice that these agencies are called in for large dollar loss fires.Fire Investigator Chip Premus.