An investigation has been launched following claims a booklet listing which prisoners are inside for sex offences got into the hands of an inmate at a Salford jail.
The inquiry is being carried out at Forest Bank Prison in Agecroft.
It is alleged the security breach has caused some inmates to fear for their safety.
A source told the Manchester Evening News said: "It was brought to my attention by an inmate that a booklet kept by the prison staff in a locked office has been found in the hands of an inmate.
"This booklet states which prisoners are in for sex offences and on suspicion of sex offences including ones on remand, so are still innocent until proven otherwise.
"This is information that should never have left the staff office."
The M.E.N. understands an inmate told another on Wednesday that he had seen his name in a booklet - and showed him the booklet the next day.
Matt Spencer, director at Forest Bank Prison, said: "We take all security matters at the prison extremely seriously and while we cannot comment on specific details, we are investigating this matter and will take all appropriate actions needed."
Earlier this week, it was revealed an inmate at Forest Bank had died.
It is understood the inmate had an existing illness.
An HMP Forest bank spokesperson said: “We can confirm that a prisoner from HMP Forest Bank passed away at Salford Royal Hospital on Tuesday, 8th June. Our thoughts are with his family and it would be inappropriate to comment any further at this stage."
As a death in custody, it will be investigated by the Independent Prisons and Probation Ombudsman.
The Category B prison has capacity for 1,460 prisoners and is run by Sodexo Justice Services.
