An estimated $200,000 worth of damage was done to the Orana Juvenile Justice Centre in Dubbo after four detainees armed themselves and engaged in a seven-hour stand-off with staff.
The detainees' revolt began when they climbed a 12-metre high fence and got onto the roof of a building on May 1.
The Daily Liberal can reveal the out-of-control youth wreaked havoc from 4.40pm until 11.54pm, when they finally chose to get off the roof of the taxpayer-funded centre.
Centre staff called police for help at 9.30pm, five hours after the detainees got on the roof.
A NSW Police source said the detainees reportedly armed themselves with broken structures, removed roof paneling and destroyed building foundations during the stand-off.
"It is fortunate that no one suffered any serious injury," the source said.
"The incident posed a significant risk to numerous staff members.
"CCTV footage has been supplied to police and the incident is under investigation."
No charges have been laid and the final damage bill is being calculated by assessors.
"The safety and well-being of staff is Juvenile Justice's number one priority," a Juvenile Justice spokeswoman said.
"Staff worked to de-escalate the situation and negotiate with the young people to come down voluntarily.
"There were no injuries to either young people or staff."
The Daily Liberal asked Gareth Ward, the state government minister now responsible for Juvenile Justice, if the training was delivered before the incident took place.
A spokesperson for Mr Ward declined to answer the question.
Juvenile Justice is reviewing the incident.