Published Friday, 14 December 2012
The incident is understood to have happened on Thursday. (© UTV)
Johnny Sandhu was arrested in 2006 after police taped conversations he had with his clients - suspected loyalist paramilitaries.
Police have confirmed a prisoner at the jail was attacked on Thursday.
A PSNI statement said: "Police in Limavady received a report of an attack on an inmate in Magilligan Prison on Thursday 13th December.
"An investigation is being carried out and enquiries are ongoing."
The Prison Service said the attack was carried out by an inmate, adding it can make "no further comment" during the course of the investigation.
A statement said: "The Prison Service can confirm that a prisoner was assaulted by another prisoner at Magilligan Prison yesterday.
"This is now the matter of a police investigation and we can make no further comment."