Ian Watkins, the former Lostprophets singer who is a decade into serving a 29-year sentence for child sex offenses, was stabbed in prison on Saturday. As Sky News reports, Watkins sustained several “not life-threatening injuries” after being taken hostage by three other inmates. Watkins was freed by guards six hours later at HMP Wakefield in West Yorkshire, the high-security prison where Watkins is being held.

“Police are investigating an incident which took place on Saturday at HMP Wakefield,” a prison spokesperson said in a statement to Sky News. “We are unable to comment further while the police investigate.”

In 2013, Watkins was convicted on numerous sex offenses, including the attempted rape of a baby.