The agency released 16 images on Tuesday, drawn from memory by Samuel Little, who told authorities they are just some of the more than 90 people he killed over three decades.
“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 FBI spokesperson Shayne Buchwald. “We want to give these women their names back and their family some long awaited answers. It’s the least we can do.”
The strategy has worked before, Buchwald said. Women who appeared in two previously released portraits were identified, he said.
Little, 78, confessed to about 90 killings last year while serving three consecutive life sentences for murder, the FBI announced last year.
The killings occurred across the country, from Los Angeles to Miami, Houston to Cleveland, all between 1970 and 2005.
He remembered where he was, what car he was driving and could even draw pictures of the women he killed, the FBI said. He was less reliable on the dates of those incidents, however, the FBI said.
How the story was revealed
Little, also known as Samuel McDowell, was already in prison last spring when his name came up in the FBI’s Violent Criminal Apprehension Program, known as ViCAP, in connection with a series of unsolved murders across the country. One killing in Odessa, Texas looked especially relevant.
So, Texas Ranger James Holland along with two FBI crime analysts traveled to California where Little was being held for beating and strangling three women and dumping their bodies in an alley, dumpster and a garage, according to the FBI.
Holland was trained in cold cases and visited Little, gaining his trust over time, Bland said.
Now in poor health, Little is in custody in California, according to Ector County DA Bland.
No formal charges on any of the additional killings have yet been brought.
CNN has reached out to E.J. Leach, the attorney representing Little in the Texas case, and has not yet received a response.
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.
Correction: This story has been updated to accurately reflect the conditions under which Little could become the most prolific serial killer in US history. It has also been updated to reflect that Little is in custody in California.
CNN’s Eric Levenson and Chuck Johnston contributed to this report.