Detainees at a Sydney youth justice centre have spent more than six hours atop a roof in a stand-off with no clear motive.
The six boys scaled the roof just before 5pm at Cobham Juvenile Justice Centre in Werrington on Wednesday.
The incident was being handled internally and a full investigation into how the youths made it onto the facility would be conducted once they were back on the ground, a Juvenile Justice NSW spokesman said.
They've missed dinner and now are sitting in the dark, he said.
Public Service Association of NSW said three of the boys were high-risk offenders.
It's believed one was recently involved in a similar incident at a youth justice centre in Dubbo.
PSA general secretary Stewart Little said the standoff at Cobham "is just the latest in what PSA has been warning about."
Staff at the six NSW juvenile justice centres walked off the job on Wednesday for two hours over what they say is increasing violence in the system and a lack of a unit for high-risk offenders.
Corrections Minister David Elliot this week said youth officers have the challenging task of managing some of the most complex young people in the state.
He pointed to a national security interest register for certain detainees, $1 million in de-escalation and negotiation training, and CCTV upgrades as investments the state government have recently made.