Ian Watkins, the former lead singer with Lostprophets who was jailed for 29 years for child sex offences, has reportedly been stabbed at HMP Wakefield.
He is said to have been taken to hospital after being stabbed at the prison in West Yorkshire.
A source told the Mirror he had been taken hostage by three other inmates on Saturday morning.
A Prison Service spokesperson said: “Police are investigating an incident which took place on Saturday at HMP Wakefield.
“We are unable to comment further while the police investigate.”
Watkins was jailed for 29 years in December 2013 with a further six years on licence, after admitting a string of sex offences – including the attempted rape of a fan’s baby.
The disgraced singer was arrested following the execution of a drugs warrant at his Pontypridd home on 21 September 2012 when a large number of computers, mobile phones and storage devices were seized.
Analysis of the equipment uncovered Watkins’ depraved behaviour.