Security in Western Australia's youth detention facilities is under scrutiny as further details emerge of violence at Perth's Casuarina Prison.
The West Australian Department of Justice confirmed a youth custodial officer was injured in Unit 18 at the prison on Wednesday and provided information on a second incident involving a fire on the same day.
The officer received treatment for his unspecified injury which the department said was not a broken arm, contrary to concerns raised by the Community and Public Sector Union (CPSU).
In the separate incident, the department said staff responded to a detainee causing damage to a cell.
The detainee had set paper and books alight but officers were able to quickly extinguish the flames.
"Three youth custodial officers escorted the detainee to hospital where the detainee was checked for smoke inhalation," a statement said.
"The detainee was returned to the unit the same day. No officers required treatment offsite for smoke inhalation."
The disturbances came after six guards were allegedly injured on Sunday when inmates freed themselves from their cells.
While Casuarina is an adult prison, Unit 18 is being used to house youths who had proved difficult to manage at the Banksia Hill Juvenile Detention Centre.
CPSU assistant secretary Melanie Bray said the continued threat to officers was a dark shadow over the successful ballot of members, which this week accepted the state government's offer on a new industrial agreement.
The new agreement includes a commitment to baseline measures to begin addressing the workplace health and safety concerns held by officers at Banksia Hill.
The union said the new regimen did not currently apply to workers or incidents at Unit 18.
"Members have made significant wins for baseline safety measures over the past year, and these incidents continue to highlight how incredibly unsafe these working environments are and how important it is to make safety a priority," Ms Bray said.
"We urge the Department of Justice to continue to work with our members to continue to develop and implement safe solutions.
"Safety must be the first and last consideration at both youth custodial estates."
The department said while there had been staff injuries during a number of recent incidents, on no occasion over the past two weeks had any officers at Banksia Hill or Unit 18 been required to be "escorted in an ambulance".
"Any assaults on staff by persons in custody is unacceptable," it said.
"The Department of Justice is continuing to assess operational security in youth custodial facilities to enhance the safety of staff and detainees at the sites."
In Sunday's unrest at the Casuarina jail, two inmates allegedly stole the keys to the accommodation areas and freed 11 others from their cells, before climbing onto the roof and damaging property.
Six guards were injured, debris was thrown at staff, three buildings were damaged and one flooded before order was restored.
Responding to that incident, Premier Mark McGowan described it as appalling and shocking and said those involved would face charges.
