"We are hoping that someone - family member, former neighbor, friend - might recognize the victim and provide that crucial clue in helping authorities make an identification", said Federal Bureau of Investigation spokesperson Shayne Buchwald.
Samuel Little, 78, sparked investigations into cold cases in several U.S. states after he began confessing to the crimes last May.
Officers are said to be desperately scouring old case files and photographs to try and identify the Jane Does, but matching them up is proving to be a hard task.
Late a year ago, investigators had released two of Little's portraits, in hopes of identifying the women.More news: Strong storm brings damage - and snow - to Hawaii
Pearl Nelson, 38, left, is holding a photo of her mother victim Audrey Nelson, as she is hugged by Mary Louise Frias, whose Godmother, Guadalupe Apodaca Zambrano was also a victim of convicted serial killer Samuel Little as they are surrounded by family of his victims following Little's sentencing.
Sam Little, 78, said he aimlessly murdered an innocent person in 1970 and repeated the act 92 more times over the next 35 years, before halting his sickening tirade in 2005.
Investigators are now said to be encouraging Little to continue with his twisted artistic endeavor in the hope of bringing retrospective justice to those whose brutal deaths were once drastically overlooked.
If all 90 confessions are confirmed, Little would be the most prolific known United States serial killer. But starting last May, Little shared story upon story of the dozens of other vulnerable women - many of whom were involved in prostitution and addicted to drugs - who he claimed to have strangled to death, leaving a trail of bodies across the country. He remembers where he was, and what auto he was driving.
Despite Little's detailed confessions, corroboration and victim identification have proved challenging for law enforcement. For instance, one teenage victim from Miami is sporting a blue headband while a victim from Texas has purple hair.More news: More LG G8 ThinQ renders emerge, corroborate other leaks
"Over the course of that interview in May he went through city and state and gave Ranger Holland the number of people he killed in each place".
The FBI urged anyone with information about the victims to call or email analysts at the bureau's Violent Criminal Apprehension Program at 800-634-4097.
In the other three cases - one from Prince George's County, Maryland, another from West Memphis, Arkansas, and the third from Pascagoula, Mississippi - police have matched one of Little's confessions to skeletal remains and corresponding case files.
Now in poor health, Little is in custody in California, according to Bland.
CNN has reached out to E.J. Leach, the attorney representing Little in the Texas case, and has not yet received a response.More news: Assassin’s Creed III Remastered for Switch now listed on Ubisoft’s website
Little was caught after being arrested on a drugs charge in a homeless shelter in Kentucky, and extradited to California in 2012.