The detainees were seen throwing rocks at passing cars on Glenfield Road and attempting to damage the roof and barbed wire with a metal pole. 

One detainee is understood to have injured his leg and NSW Fire and Rescue crews are attending the scene. 

“Juvenile Justice Centre are currently negotiating with two detainees, who gained access to the roof of Riverina Juvenile Justice Centre just before 9.30 this morning,” a spokesperson from Juvenile Justice said. 

It is understood that the two detainees are still on the roof. 

This marks the second incident this year where juvenile detainees have managed to scale a juvenile justice centre roof in NSW, with six young offenders staging a 10-hour standoff at Cobham Juvenile Justice Centre last month. 

Public Service Association general secretary Stewart Little has been in talks with the Berejiklian government over therapeutic units in juvenile justice centres to better manage high-risk detainees.

“Today’s standoff at Riverina Juvenile Justice Centre is the second in as many months and reinforces the urgent need for therapeutic centres in our juvenile justice centres to manage high-risk detainees,” Mr Little said.

Mr Little blamed the NSW government’s “lack of proper investment” in rehabilitation for juvenile offenders. 

“This means that you have the worst-of-the-worst leading young offenders astray and our members are constantly at risk of violence, because there is no appropriate management of detainees based on their risk level,” he said. 

“Even as the number of young offenders drops the violence in juvenile justice centres is rising because there is no investment in training and proper rehabilitation facilities for young offenders.

"We're also calling for the reintroduction of high-risk offender units, to help minimise the risk of particularly violent detainees.

"We have been in ongoing negotiations with Corrections Minister David Elliott, but today's standoff reinforces just how urgent the need for therapeutic centres is,” he said.