Advances in technology have allowed suitable DNA samples to be collected from the remains of eight unidentified male victims, Cook County Sheriff's office said in a news release Wednesday.
Police say some of Gacy's identified victims were never reported missing because family members were unaware they were gone. Police said they believe the eight unidentified victims also went unreported, perhaps because they were estranged from family.
The sheriff's office is encouraging people who had a blood relative go missing to donate a DNA sample, even if they are not from Illinois, since Gacy targeted bus stations looking for victims who were traveling.
Gacy was executed in 1994 for killing 33 young men and boys, the bodies of whom were found in the crawl space of his suburban Chicago home and in the Des Plaines River.
Notable deaths of 2014 [PHOTOS]