The Northern Territory Department of Corrections has contradicted police reports of a riot in the Darwin juvenile detention facility.
Police Duty Superintendent Helen Braam told AAP on Monday that police received a report about 4.30pm on Sunday that eight boys had refused to go back to their rooms from a common area.
A group of boys - which the department numbers at four - smashed a pool table, using pieces of debris as weapons to break glass in the viewing windows, and then using the table as a barrier blocking the staffroom door.
Police say the boys used metal louvres from their rooms as weapons to damage property and threaten staff, and then smashed a hole in the ceiling, which one boy crawled through to access the dining room.
The group used a toaster to start two fires in the common area, Duty Supt Braam said.
However, the department says only one fire was lit.
"Of the six detainees in the block, only four were involved in the disturbance during which some windows and other fittings were damaged, an attempt was made to set fire to a mattress that was quickly doused with water and a detainee managed to get into a roof space, however the security of the block was not compromised," Acting Commissioner Rosanne Lague said in a statement.
She said "staff managed the situation professionally with no injuries to either staff or detainees", but police said one boy was expected to be charged with aggravated assault after kicking a guard in the groin.
Prison officers forced entry and got the boys out by 7pm, before they could be harmed by the smoke and fire.
Fire and Emergency Services also attended, Ms Lague said.
Duty Supt Braam says it's expected that formal charges of arson and criminal damage will be laid against eight boys.
The medium security unit of the former adult prison at Berrimah was recommissioned as a youth detention facility just before Christmas, with 21 teens moved there a month early due to violent behaviour by a group of older prisoners.
"This small group of youths continued to present the department with behavioural and management challenges similar to those they display in the community and for which they are in detention," Ms Lague said.
It is not yet known if any of the boys were involved in an earlier escape attempt in August at the previous juvenile detention centre, or during a three-hour siege later that month, when tear gas and the dog squad had to be used against six rioting teens.
That centre was closed after the government acknowledged it was not fit to hold underaged offenders.
