Investigators have linked more than 60 killings in at least 14 states to a 79-year-old California inmate who may be the most prolific serial killer in U.S. history.

Ector County, Texas District Attorney Bobby Bland said Samuel Little, also know as Samuel McDowell, continues to cooperate with investigators from around the country who interrogate him in prison about cold case killings dating back to the 1970s.

Among those who spoke to him were investigators from Ohio, where Little grew up and where he’s suspected of killing at least five women.

Little, who claims to have killed more than 90 women all over the country between 1970 and 2005, has told investigators he targeted women who wouldn't be missed right away, such as street people or prostitutes, and whose necks appealed to him for strangulation, which gave him sexual gratification.

Little was convicted of killing three Los Angeles-area women and pleaded guilty to killing a Texas woman, and he’s serving life sentences in California.

Investigators have linked more than 60 killings in at least 14 states to a 79-year-old Samuel Little, a California inmate who may be the most prolific serial killer in U.S. history. Little is shown at left in a recent photo and at right in a booking photo from 1972

Little lived a nomadic lifestyle and claims to have killed 93 women as he crisscrossed the country over the years.

Bland said Little, who celebrated his birthday behind bars on Friday, is in failing health and 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.

Little was convicted of the 1989 murder of Audrey Nelson, 35, in Los Angeles in 2014. The cold case of the 1982 murder of Rosie Hill, 20, in Ocala, Florida was closed on November 15 following Little's confession to the slaying.

During Little’s 2014 trial in Los Angeles, prosecutors said he was likely responsible for at least 40 killings since 1980.

Authorities at the time were looking for possible links to deaths in Florida, Georgia, Kentucky, Louisiana, Mississippi, Missouri, Ohio and Texas.

But Little was not forthcoming with information at the time and Bland credits Texas Ranger James Holland with gaining Little’s trust and eventually eliciting a series of confessions.

Little was convicted of the 1989 murder of Audrey Nelson, 35 (left), in Los Angeles in 2014. The cold case of the 1982 murder of Rosie Hill, 20 (right), in Ocala, Florida was closed on November 15 following Little's confession to the slaying

Little, whose health is said to be on the decline, has been talking to cold-case investigators from around the country about unsolved murders

This combination of undated sketches provided by the FBI in February shows drawings made by Little, based on his memories of some of his victims

Holland traveled to California last year to speak with Little about cold cases in Texas. That led Little to be extradited to Texas and his guilty plea in December in the 1994 strangulation death of Denise Christie Brothers in the West Texas city of Odessa.

But Holland’s conversations with Little have continued, even after Little was returned to California to serve his sentences, and it was Holland who determined that he was responsible for 93 deaths, said Bland, who received an update from Holland this week.

Information provided to Holland was relayed to law enforcement agencies in several states, leading to a revolving door of investigators who traveled to California to corroborate decades-old deaths.

Among them were investigators from Ohio, where prosecutors on Friday announced charges against Little in the 1981 killing of a Cincinnati woman and where he was charged last week in the deaths of two women in Cleveland.

'To him, strangulation was sex,' said Mark Piepmeier, chief assistant Hamilton County prosecutor in Ohio. 'That's how bizarre this person is. That struck both of us as "this cat's different than anybody we normally deal with".'

'He described it as telling a normal man that normal sexual intercourse was a crime,' said Cincinnati Police Detective Kelly Best. 'And when he got the urge, that's when he would seek out a woman and commit his crimes.'

She and Piepmeier said Little seemed to be trying his best to help them.

'He was friendly, conversational, very open, very helpful,' said Best, adding that there appeared to be nothing about him that would give 'a vibe' of danger.

Little previously confessed to killing 21-year-old Mary Jo Peyton in 1984 and 32-year-old Rose Evans in 1991, both in Ohio

Convicted serial killer Samuel Little, 79 (left), has been indicted for the murder of Anna Lee Stewart (right) in Ohio in 1981

Little previously confessed to killing 21-year-old Mary Jo Peyton (left) in 1984 and 32-year-old Rose Evans in 1991 (right), both in Ohio

Hamilton County Prosecutor Joe Deters announced on Friday that Little has been indicted for the murder of Anna Lee Stewart, who was last seen alive in Cincinnati.

Little told investigators on the day he strangled Stewart to death it was raining, so he bundled her body into his car and drove to Grove City in suburban Columbus, where he dumped the body in the woods.

Little is also charged with a second murder in Cincinnati. He confessed to killing a woman whose identity remains a mystery.

Little provided a sketch and description of the second Cincinnati woman. Deters said interns from his office are studying coroner's records in hopes of determining who she was.

He previously confessed to another killing in Cleveland, though investigators are still trying to identify the victim in that case. Deters explained that Little’s victims often were suffocated or strangled, in many cases leaving few physical marks and leading investigators to determine the women died of overdoses or of natural causes.

'There’s still been no false information given,' Bland said. 'Nothing has been proven to be false.'

Little's toll appears to have surpassed the likes of notorious American serial killers including John Wayne Gacy, Ted Bundy and Green River's Gary Ridgway.

Ridgway, the so-called Green River Killer, pleaded guilty to killing 49 women and girls, making him the most prolific serial killer in U.S. history in terms of confirmed victims, though he said he killed 71.

Little's run-in with the law date back to 1956 with a series of shoplifting, fraud, drug and breaking and entering charges.

But authorities only recently began unraveling his serial killing spree after he was arrested at a homeless shelter in Kentucky in 2012 and extradited to California to face drug charges.

When he was in custody, authorities found DNA evidence linked him to three cold case murders in Los Angeles between 1987 and 1989.

The three women had all been beaten and strangled with their bodies dumped in an alley, a dumpster and a garage. Little was sentenced in 2014 to life in prison for the three murders.

Little grew up in Lorain, in northeast Ohio and later left the area to travel the country. The FBI in February released chilling sketches drawn by Little of some of his victims based on his memories of them.

Bland said 50 cold homicide cases have been closed as a result of Little's confessions and that most of the remaining unsolved slayings occurred in California.