A man jailed for murdering a young girl has said he killed 48 people across the US, which, if true, would make him one of America's worst serial killers.
Police are taking Browne's claims seriously
Robert Charles Browne told Colorado police the killings happened between 1970 and 1995, when he was arrested for the murder of Heather Dawn Church.
The killings allegedly took place across nine US states.
Investigators have so far been able to corroborate Browne's claims in six of the murders, a police official said.
Sheriff Terry Maketa of El Paso County, Colorado, said the authorities were taking Browne's claims seriously.
"It's possible he's exaggerating, but I don't think you can conduct business assuming he's exaggerating," Mr Maketa said.
"We'll continue to pursue leads," he said.
Police showed photos of some of Browne's possible victims
Browne's confessions came after several years of correspondence and interviews between him and volunteer investigators following up unsolved murder cases.
If his claims are proven, Browne would be one of the worst serial killers in US history.
A former truck painter, Gary Ridgway, pleaded guilty in 2003 to killing 48 women - crimes that earned him the nickname, the Green River Killer.
Browne appeared on Thursday in an El Paso court to plead guilty to the murder of Rocio Sperry, whom he said he strangled in 1987.
Browne said he started killing by murdering a soldier in South Korea in the early 1970s but police say this has not been verified, the Associated Press news agency reported.
Browne reportedly first came to the attention of the police was when he was questioned over the murder of Heather Dawn Church, who went missing in 1991 and whose skeletal remains were found in a ravine.