Five cells at Hakea prison were damaged on Saturday night – the second time since late June the teenagers have damaged their rooms at the facility.
Sinks, toilets, shower areas, shelving and mattresses were all trashed, a Department of Corrective Services spokesman confirmed.
The detainees did not get out of their cells, unlike the riot at the nearby Banksia Hill Detention Centre for juveniles in January that left 108 of the facility’s 240 cells unfit for use and prompted the transfer of the inmates.
Staff and detainees were not injured in the latest incident.
The department, which is yet to estimate the cost of the damage, is investigating the circumstances of the incident and may lay criminal damage charges.
In May, 30 juveniles and five 18-year-olds were charged over the Banksia Hill riot, while one of the adult offenders was charged with two counts of assaulting a police officer.