A huge blaze has broken out at the National Youth Detention Centre in Oberstown, north County Dublin.
Residents reported seeing smoke and then flames 'billowing' from the troubled centre which houses up to 40 of the State's most dangerous young criminals.
Staff sources said a 'riot' broke out in the centre late on Monday afternoon.
The Garda Emergency Response Unit was sent to the Oberstown Centre at 9pm after youths seized control.
This followed trouble over the weekend in which substantial damage was done to a wing of the centre which was visited last week by Pat Kenny as part of a tour by the Centre's director Mr Pat Bergin.
The pair even exchanged a joke about the 're-engineering' of the Unit which was being put on display after it had been totally refurbished after previously being damaged.
The weekend violence followed by trouble on Monday morning prompted staff - after complaining about attacks, injuries and fear for their lives - to walk out in protest.
By teatime the situation in the centre was said to be getting out of control. Local people said smoke started coming from the centre at around 9pm followed by visible flames 15 minutes later.
The Garda helicopter arrived at 9.15 followed by what locals said was a succession of fire and other emergency vehicles.
One resident who could see the fire from his back garden said: "We heard sirens and more sirens and thought it might have been a crash on the (M1) motorway. Then we saw smoke billowing out of the place. Then you could see flames."
The witness added there had been consternation in the area after the previous break-out attempt earlier this month in which teenage inmates armed with golf clubs and a ladder they stole from a storeroom attacked staff and then scaled the 30ft perimeter wall. All five were quickly arrested.
One member of staff was reported to have been seriously injured and taken to hospital after being attacked by inmates. No further details were available.