The FBI is investigating a prisoner in Texas who they believe could be the most prolific serial killer in US history.
Samuel Little, 78, is currently serving life for the murders of three women – and now he has confessed to killing as many as 90 people across the country between 1970 to 2005.
Cold case detectives interviewed the former boxer after a Texas ranger who earned his trust indicated that someone else may have been killed in the Washington region in the 1970s.
He told detectives previously unreported details about an unsolved killing in Laurel, Maryland.
A body found in 1972 was never identified.
Little said he picked up the victim at Washington bus station and told him she was recently divorced, from the Massachusetts area and may be a mother. Detectives are working to identify her.
An FBI report said he mainly preyed on drug addicts and prostitutes in a decades-long murder spree.
After he was sentenced to life in 1994, Little later confessed to the 1994 murder of Denise Christie Brothers in Odessa, Texas.
Police are now working to verify the victims from his new confession – with 34 of a possible 90 verified so far.
FBI crime analyst Christina Palazzolo said he told Texas ranger James Holland the number of people he killed in each city and state.
"Jackson, Mississippi – one; Cincinnati, Ohio – one; Phoenix, Arizona – three; Las Vegas, Nevada-one…" Ms Palazzolo said.
Bobby Bland, district attorney of Ector County where Little is being held, said: "Little will be confirmed as one of, if not the most, prolific serial killers in US history."
The deadliest known US serial killer is believed to be Gary Ridgway, otherwise known as "Green River Killer", who was convicted of 49 murders and is serving a life sentence in Washington state.
According to the FBI, Little "remembers his victims and the killings in great detail" but is "less reliable, however, when it comes to remembering dates".
Since most of his victims were drug addicts and prostitutes, in some cases the deaths were never investigated.
His method of killing "didn't always leave obvious signs that the death was a homicide," the FBI said.
"The one-time competitive boxer usually stunned or knocked out his victims with powerful punches and then strangled them.
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"With no stab marks or bullet wounds, many of these deaths were not classified as homicides but attributed to drug overdoses, accidents, or natural causes."
The FBI said Little is in poor health and is likely to spend the remainder of his days in prison in Texas.