An attack on a prison guard in regional Western Australia by an inmate who jumped a fence and started throwing rocks has prompted a warning from the union, but the state government says the facility's staffing levels are appropriate.
The WA Prison Officers' Union has expressed alarm about the incident at West Kimberley Regional Prison in Derby, in the state's north, last Thursday.
The guard had been trying to restrain a prisoner when he was punched and knocked to the ground by another inmate, the union says.
The two prisoners then jumped an external fence and began throwing rocks and smashing windows.
Another two joined in and scaled the roof of the prison, causing minor damage before they were negotiated down.
The Department of Justice says the incident was resolved within two hours and no prisoners were injured.
All four prisoners involved in the incident are expected to face disciplinary charges.
WA Prison Officers' Union secretary Andy Smith on Monday said the incident had the potential to be far worse, noting that it would have taken the Special Operations Group at Perth's Hakea prison more than six hours to arrive.
He claimed the state's prisons were "understaffed and unsafe" because of restrictions on overtime, a claim rejected by the government.
"There are currently no overtime controls at the prison," a Department of Justice spokesperson said.
"Since the commencement of open ended recruitment, more than 500 additional prison officers have been hired across the state including officers from regional centres."
The government launched a recruitment drive for prison officers last year following riots at Greenough Regional Prison in 2018.
Authorities were forced to build a high-tech electric fence to separate male and female prisoners at Greenough after violent rioters broke into the women's compound in 2018, while 10 inmates escaped after climbing the roof.
The 12-hour riot caused millions of dollars worth of damage, with detainees starting fires and using weapons against guards.
"We need to learn from what happened in Greenough and keep both our community and prison staff safe by staffing prisons adequately," Mr Smith said.
The Department of Justice said Greenough and West Kimberley were "very different facilities".
"All prison officers are trained in riot control and there are a number of staff who are able to respond, cordon and contain where needed," the spokesperson said.
"Derby Police are also able to provide an immediate response in accordance with the Emergency Management Plan for the area and are equipped to assist the prison during any unrest."
Australian Associated Press