(MCT) — CHICAGO — More than two years after reopening the John Wayne Gacy case, Cook County, Ill., sheriff’s investigators continue to probe cold case files from across the country and leads closer to the home in search of additional victims of the notorious serial killer who was executed nearly two decades ago.

Among the investigative avenues investigators are now pursuing is the case of two teenage boys who were raped and slain in Michigan in the 1970s when Gacy’s killing was at its height and he was believed to have traveled to Michigan. Sheriff Tom Dart said in a speech Tuesday that investigators are trying to determine if a DNA match can be made while also studying Gacy’s travel records.