A West Australian prison escapee remains on the run after a mass breakout during a riot that left the jail looking "like a war zone".

Ten men escaped from Greenough Regional Prison near Geraldton in WA's Mid West on Tuesday afternoon.

Nine prisoners have been recaptured but Bradley Silvester, 35, remains at large.

After seven escapees were found in the area, Brendan Bartley, 22, and 18-year-old Darryl Councillor handed themselves in to local police.

Prison Officers' Union acting secretary Paul Ledingham said the riot went for hours and was finally contained early today.

"It's utter devastation," Mr Ledingham told reporters.

"We've seen staff control rooms - supposedly secure areas for staff - smashed, destroyed and in one case burnt, fully burnt out.

"There is bricks, debris."

He said prisoners got hold of maintenance equipment including angle grinders, which they used to get into the female unit.

Premier Mark McGowan, who toured the trashed facility, said some of the women participated in the riot and their unit now appeared uninhabitable.

"Somehow this group mentality took hold," he told reporters.

There were no reports of any sexual assaults.

Power tools were used to cut a lock off an inner fence and the escapees then used a ladder to scale the outer fence.

"They were organised," Mr McGowan said.

"It looked like a war zone in there."

He said the damage bill would run into the millions.

Mr McGowan said the lives of some prisoners were at risk from fire and smoke during the riot.

Three guards were pepper-sprayed and molotov cocktails were thrown.

It is believed prison officers lost control when they went to extinguish a cell fire that was sparked as a diversion.

Other fires were then lit.

Mr Ledingham said state budget pressures had led to understaffing at WA jails despite the muster being at a record, over-capacity high and regional facilities were among the worst affected.

He called on the state government to "immediately" recruit more staff, saying most WA prisons were "a powder-keg ... ready to explode".

"According to our members, this has been brewing for some time," Mr Ledingham said.

Mr McGowan said there had been no indication of rising unrest among the inmates but there would now be 'heightened monitoring" at WA prisons.

The CPSU said senior Corrective Services executives had been warned the situation across all WA prisons was "dire" including treatment courses not being run and prisoners spending large amounts of time in cells.

An extra 150 officers were sent to Geraldton to help search for the escapees.

Residents and drivers were warned to not approach them and urged to lock their doors and windows.

The jail holds remand prisoners under maximum security while other inmates are kept in medium and minimum security sections.

The escapees will be moved to Hakea remand prison in Perth, Mr McGowan said.

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