DULUTH, MN (KDAL) - The Duluth Police and Fire Departments are investigating a fire at an abandoned and vacant house at 3605 Piedmont Avenue early Wednesday morning.  Arson investigators have determined that the suspect made a forced entry through the back door of the house and the fire left the building a complete loss.  Anyone who might have seen something suspicious in the area between 12:15 and 1:15 a-m Wednesday is asked to call Duluth Police or the Arson Hotline at 1-800-723-2020.