Confessed serial killer now linked to 60 deaths in 14 states: Report Prosecutors say they are racing to crack unsolved cases.

A confessed serial killer who claims to have left a trail of women's bodies in a decades-long, cross-country killing spree from Florida to California has now been linked to 60 deaths, a Texas prosecutor said on Friday, according to The Associated Press.

Samuel Little, 79, is serving life sentences for killing three women in Los Angeles, and has been cooperating with federal officials and authorities in a sprawling series of investigations in multiple states for some time now. As far back as last fall the FBI described him in a report as "among the most prolific serial killers in U.S. history."

At the time, authorities said they had linked him to 36 murders.

Little -- who claims his killing spree stretched from 1970 to 2005 -- is in poor health, so investigators are racing to identify as many of his victims as possible and help close as many unsolved cases as possible.

Ecton County District Attorney Bobby Bland said Little has exhausted his appeals, leading him to be forthcoming with investigators.

"At this point in his life I think he’s determined to make sure that his victims are found," he said, according to the AP.

In February, the FBI released 16 portraits drawn by Little based on his memories of his victims. The agency has also released a map showing the incidents linked to unidentified victims.

Little's confessions that have not yet been corroborated by law enforcement.

Last fall, FBI officials told ABC News that it is was working with the Department of Justice’s Bureau of Justice Assistance, the Texas Rangers and dozens of other state and local law enforcement agencies "to match Little’s confessions with evidence from women who turned up dead in states from California to Florida between 1970 and 2005."

Little's life of crime spanned decades, according to FBI officials. After dropping out of high school in Ohio, Little "lived a nomadic life" and was first arrested in 1956, according to the FBI. He displayed a "dark, violent streak" in his many crimes, which included shoplifting, fraud, drug charges, solicitation and breaking and entering, FBI officials said.

FBI officials said the challenge in connecting the dots is partly due to the fact that Little moved around frequently and often preyed on vulnerable women, some of whom were believed to be involved in the sex trade or addicted to drugs.

Little, who was once a competitive boxer, often knocked out his victims and then strangled them, sometimes leaving no clear signs of a homicide, according to the FBI. Many of their deaths were attributed to natural causes, overdoses or accidents, officials said.

In 2012, Little was arrested at a Kentucky homeless shelter and extradited to California on a narcotics charge, the FBI said. That's when police in Los Angeles matched his DNA to three unsolved murders from the late 1980s in which all three women were killed the same way, according to FBI officials.

"In all three cases, the women had been beaten and then strangled, their bodies dumped in an alley, a dumpster, and a garage," the FBI said in its report.

After linking his DNA to those crimes, police in Los Angeles asked the bureau's Violent Criminal Apprehension Program (ViCAP) for a full background report on Little, and "the FBI found an alarming pattern and compelling links to many more murders," according to the report.

Authorities are using the same program to help connect the dots on other crimes.

Despite asserting his innocence, Little was convicted and sentenced to three consecutive life sentences without the possibility of parole for the California killings in 2014, the FBI said. He appealed the life sentences but lost, the AP reported.