Two notorious Limerick brothers serving life for separate murders have threatened the governor of Mountjoy Prison after they were moved to the Challenging Behaviour Unit (CBU) as punishment.
Killers Wayne and Dessie Dundon have recently been moved from the maximum security Portlaoise Prison to Mountjoy because of their reputation for non-cooperation and accumulating contraband.
Insiders say they are "not happy" about having their privileges revoked for a 40-day period as part of their punishment.
It was reported at the beginning of the month that Wayne was found with phones, steroids, weapons, syringes and mobile phone SIM cards in his cell.
The decision to move the brothers was taken in view of the fact that security had failed to prevent access to contraband phones and drugs.
They were issued with P19 reports for their actions and behaviour in Portlaoise.
These are handed to prisoners who have broken prison regulations and can lead to various punishments, depending on the severity of the misdemeanour.
For the Dundons, this meant incarceration in the CBU and revoking of their privileges.
The CBU is used to house troublesome inmates and separate them from the wider prison population when they become aggressive or disruptive.
"The pair were moved into the unit on Thursday after their P19s were processed and dealt with," said a source.
"They were not at all happy with the decision and threatened Governor Brian Murphy.
"It seems a car belonging to a governor from Portlaoise Prison was damaged in the past and they told Mr Murphy the same would happen to him, or worse, and they threatened that things are going to escalate," the source added.
"There were also rumours that they had threatened him the day before as well, which won't help their case at all."
It is understood that on a previous occasion, when he was moved to Mountjoy, Wayne Dundon thrashed his cell to express his displeasure.
"There is tension in the air in the jail now but the officers are the ones exposed to most risk because they are the ones who have to keep a lid on it all," said the source.
The Irish Prison Service said it could not comment on named individuals.
Dessie (34) was sentenced along with four others to life in prison in December 2003 for the murder of Limerick crime boss Kieran Keane, and the attempted murder of his nephew, Owen Treacy, in Limerick a year earlier.
Wayne (39), from Lenihan Avenue, Prospect, Limerick, and another man, Nathan Killeen, of Hyde Road, Prospect, were sentenced to life behind bars for the murder of innocent businessman Roy Collins in Limerick in 2009.
They pleaded not guilty at the non-jury Special Criminal Court to the murder of Mr Collins at Coin Castle Amusements, Roxboro, on April 9, 2009.
Mr Collins, a 35-year-old father of two who was engaged to be married, died in hospital a short time after he was shot.
His father, Steve Collins, was believed to have been the intended target due to his involvement in a previous successful prosecution against Dundon for a threat to kill.
In July 2014, the three-judge Special Criminal Court found Wayne had ordered the murder from prison and that Killeen was the getaway driver.
In March this year, Wayne failed in his attempt to get a different panel of judges to hear an appeal against his conviction for the murder of Mr Collins.
Another brother, John Dundon (33), is also serving a life sentence in Portlaoise Prison for the murder of innocent rugby player Shane Geoghegan, who was shot dead in a case of mistaken identity in November 2008.