(CNN) -- More than three decades after the arrest of serial killer John Wayne Gacy, authorities in Chicago have launched a new effort to identify eight of his 33 victims.
The Cook County Sheriff's Office says new technology has allowed it to obtain DNA profiles for the eight victims, whose remains were recovered from Gacy's house in late 1978 and early 1979 but were never identified.
"These were eight young men who had futures, and one of the most evil people to ever be on this planet destroyed their lives," Sheriff Thomas Dart said Wednesday.
Gacy was convicted in 1980 of raping and killing 33 boys and young men he had lured into his home over a period of six years, promising them construction jobs, drugs and alcohol, or by posing as a police officer or offering money for sex.
Twenty-eight of the bodies were discovered under and around Gacy's home, with most found in the 40-foot crawl space beneath the house and garage. Gacy said there were four others he had thrown into the Des Plaines River.
Gacy was put to death in 1994.
The latest effort to identify the eight victims began this year when the sheriff's office decided to clear dozens of the department's cold case investigations. The eight unknown Gacy victims make up the department's largest cold case, so Dart approved their exhumations in order to obtain new DNA evidence and, if possible, identify them.
Authorities used the DNA samples to compile profiles of each of the eight victims. It shows that they are white males between 14 and 32 years old, and authorities have even listed the approximate dates of their disappearances.
The department is now seeking family members who had a male relative go missing in the 1970s and are willing to donate a DNA sample for comparison.
"The public coming forward will allow us to do DNA matches that were not available 30 years ago," Dart said Wednesday. "It's not intrusive. It's something that is very straightforward. We have hot lines, websites set up for people to contact us, and in short order, we can conduct any of the matches that need to be done."
After Gacy's arrest, authorities learned that some of his identified victims had never been reported missing, the sheriff's office said. One reason was that the victims had been estranged from their families.
Another possible reason is that the relevant missing persons reports never made it to Chicago. Gacy was known to have targeted bus stations, the sheriff's office said, seeking victims who were traveling.
Those interested in giving a DNA sample can contact the Cook County Sheriff's Office at 1-800-942-1950 or www.cookcountysheriff.com.