Minister for Justice Michael McDowell has said there were "very disturbing" features surrounding the murder of an inmate in a holding cell in Mountjoy Prison on Tuesday morning.
He said part of the independent inquiry into the death of Gary Douch (21), Tallaght, Dublin, would focus on staffing and supervision issues in Mountjoy.
This follows reports that Mr Douch was subjected to a sustained beating in a holding cell before his death.
Under prison regulations the cell should have been checked by staff every 15 minutes.
"I don't want to get into the blame game at this stage, I think I should wait for the report," Mr McDowell said. "But if some of the reports are true that this incident took over an hour, then obviously there is an issue in relation to supervision."
The independent inquiry, which is being headed up by the former deputy secretary of the Department of Justice Michael Mellet, will also examine many other aspects surrounding Mr Douch's violent death.
"There are issues in relation to the choice of people in that room . . . whether some people should have been dealt with differently."
Mr Douch was serving a three-year sentence for assault and drugs offence. A heroin addict, he had been in prison since 2004. On Monday he requested a transfer from C1 wing to a protection cell in the basement because he feared for his own safety.
He was sharing the cell with six other prisoners, one of whom beat him and strangled him to death before smearing excrement on him. None of the other inmates raised the alarm and prison officers only realised what had happened when Mr Douch failed to emerge from the cell at 6.30am on Tuesday for breakfast.
The man who attacked him, a 23-year-old from Coolock, Dublin, is awaiting trial for robbery. He had been housed in Cloverhill Prison but was transferred to the Central Mental Hospital in the last fortnight before being returned to Cloverhill.
He was then transferred to Mountjoy on Sunday.
He was held in the holding cell on Sunday and Monday nights because the prison was over- crowded and no suitable bed could be found for him.
Unlike Mr Douch, he had not been placed in the holding cell for protection purposes.
The man, who has a history of violence, was arrested in the prison on Tuesday afternoon. He was questioned by gardaí at Mountjoy Garda station before being returned to the prison.
He was transferred back to Cloverhill last night and is expected to be sent to the Central Mental Hospital as early as today. He has admitted to the killing.
Gardaí are investigating whether the man they have questioned had tried to encourage other inmates in the cell to become involved in the attack.
It appears he tried to encourage them to attack the dead man's body as it lay lifeless.
Detectives have interviewed the other inmates in the cell and a full technical examination of the scene has also been carried out.
Mr McDowell said the issue of inmates sharing holding cells in Mountjoy pending transfers to other parts of the prison had already been brought to his attention.
"The Inspector of Prisons had reported on that before and I had asked that his criticisms should be acted upon. I want to know whether that was done. But I understand that on this occasion a number of people were in that situation for a number of days and that's another issue."
Mr McDowell said he was was anxious that the independent inquiry should be concluded quickly.
An internal inquiry in Mountjoy is also under way and gardaí are conducting a murder investigation into the killing of Mr Douch.