A 24-year-old man from Dublin died this evening following an attack in Mountjoy Prison.
The part of the D wing landing in Mountjoy jail where Derek Glennon was fatally stabbed remains sealed off as the garda investigation into his murder continues.
Glennon was serving five years for escaping from custody while serving another sentence for manslaughter.
He got into a row with another inmate but was stabbed in the side and pronounced dead shortly afterwards at the Mater Hospital.
The Director of the Prison Service said the incident occurred 'out of the blue' and even though six or seven prison officers were at the scene within seconds they were unable to save Derek Glennon's life.
Brian Purcell said the prison service had to balance security with a humane prison system but said it was virtually impossible to ensure a risk-free prison regime.
