Soham murderer Ian Huntley remains in a serious condition following a prison assault, police have said.
He was taken to hospital after being found in a pool of blood following an alleged attack by an unknown inmate on Thursday.
A Durham Constabulary spokesperson said there had been no change in the 52-year-old's condition overnight.
"He remains in hospital in a serious condition," they added.
Police earlier said that a man in his mid-40s was being investigated over the incident.
"He has not been arrested at this stage but remains in detention within the prison," the force added.
Huntley killed 10-year-olds Holly Wells and Jessica Chapman in Soham, Cambridgeshire, in August 2002.
The latest incident is not the first time Huntley has been attacked at HMP Frankland.
In 2011, an inmate who slashed Huntley's throat with a makeshift knife was jailed for life.
Damien Fowkes was sentenced to a minimum of 20 years for the attempted murder of Huntley in March 2010 and the manslaughter of child killer Colin Hatch.
Fowkes inflicted a wound seven inches long on Huntley's neck and the court was told it was only "good fortune" that the weapon missed anything vital.
The disappearance and murders of schoolgirls Holly and Jessica captured the attention of the nation in 2002.
Huntley killed them after they left a family barbecue to buy sweets, and then dumped their bodies in a ditch.
He was their school caretaker and put himself forward as a volunteer to help search for them after they went missing - and was interviewed by reporters on camera.
The efforts to locate the girls in the 13 days after they disappeared have been described as one of the most intense and extensive in British criminal history.
Huntley was convicted of murdering both girls in December 2003 and sentenced to two terms of life imprisonment.
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His girlfriend, Maxine Carr - the girls' teaching assistant - had knowingly provided Huntley with a false alibi.
She was jailed for three-and-a-half years for conspiring with Huntley to pervert the course of justice.
(c) Sky News 2026: Soham murderer Ian Huntley remains in a serious condition after prison attack
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