A woman whose car was approached by two men believed to be among 10 prisoners who escaped from a jail in WA's Mid West has told how the pair tried to wave her down and get inside her vehicle.

The inmates escaped from Greenough Regional Prison near Geraldton during what Premier Mark McGowan has described as a riot at the facility on Tuesday afternoon.

Nine of them have since been recaptured or have handed themselves in, with 35-year-old Bradley Silvester the only prisoner still on the run.

Police say Alan McDonald was recaptured but Bradley Silvester remains on the run. ( Supplied: WA Police )

Anne, who did not want her surname used, said she had just dropped her husband at Geraldton Airport and was returning home along a quiet road around 5:20pm when two men wearing green uniforms tried to flag her car down.

"I quickly locked the car and then they grabbed the bonnet of the car and they approached to the doors and tried to open both doors," she said.

"I quickly sped off and one of the guys on the left hand side tried to bang on the window of the car."

Anne had not known of the breakout at the time and initially thought the men were hitchhikers. But she quickly became suspicious about their clothing and their behaviour.

"I was like 'it's not right', but I don't know actually what I should do," she said.

"I don't want to run them down, I don't want to hurt people, but I don't know what I'm supposed to do."

Anne managed to drive away from the men and alert police.

Nine of 10 escapees back in custody

Of the 10 original escapees — who police described as "unpredictable" and potentially violent — five were recaptured yesterday while five remained at large overnight.

Two of those remaining escapees — 23-year-old Devon Comeagain and 28-year-old Alan McDonald — were recaptured this morning at houses in the area.

Two more — Brendan Bartley, 22 and Darryl Councillor, 18 — handed themselves at Geraldton police station at 1:00pm today.

The mother of a prisoner not involved in the escape said her son had called her and told her prisoners were "running amok" and smashing windows.

In a Facebook video post, she said her son was on the female side of the prison because of the melee on the men's side.

"He's over in the female side watching because … the blokes are all smash (sic) windows, wicked, they're all running amok inside the prison itself," the mother said.

"There's nobody locked away, they're all running, and running a big muck.

"I just hope that they stay on that female side or try and lock it all up the best way they can."

Millions of dollars in damage, jail like 'war zone': Premier

Mr McGowan visited the prison on Wednesday afternoon after the riot.

"To me, it looked a bit like a war zone in there, and it's obviously dangerous for officers and dangerous for the prisoners who weren't part of what was going on," he said.

"Clearly what has occurred here has been a riot, a major riot — the likes of which we haven't seen for some years in Western Australia."

He said rocks and gardening tools were used by prisoners in the riot.

"This is unacceptable, crazy, shocking, dangerous behaviour, damaging public property, risking people's lives … it is not the sort of thing we accept in this state," the Premier said.

He said prisoners had used power tools and a ladder to escape and were "organised in what they did".

Smoke was seen rising from Greenough Regional Prison during the incident. ( ABC News: Jessica Hayes )

Mr McGowan said the female unit of the prison had been severely damaged, with the overall repair bill expected to run into the millions.

He promised there would be full investigation into the riot, and said images from inside the jail would be made public.

WA Prison Officers Union (WAPOU) acting secretary Paul Ledingham said three officers were sprayed with a chemical spray during the riot.

"Reports this morning are there is extensive, extensive damage within the prison," he said.

"There's units out of action, there were for large parts of the night dozens of prisoners uncontained within the prison."

Public urged to lock doors, stay on alert

Police had earlier urged the public to lock doors and windows, and drivers were warned to keep their car doors locked.

Inspector Geoff Desanges warned residents to take care.

"These people should be treated as unpredictable and [with the] potential for violence," he said.

More than 150 extra officers had been sent to Geraldton to assist local police, and the police air wing and police dogs were helping with the search.

Sorry, this video has expired Public to urged to lock doors, stay alert

Police were notified of the disturbance about 4:30pm on Tuesday and issued a warning about an hour later that inmates may be in the surrounding area.

Alerts were sent to residents via text messages and automatic phone calls, telling them to lock up and report anything suspicious.

A text message was sent to Geraldton locals warning them to take extra security precautions. ( Supplied )

Witnesses reported seeing smoke and spotlight beams coming from the prison during the disturbance, as well as hearing yelling and the sound of a megaphone.

Roads leading to the facility were blocked, while an ambulance entered the prison during the evening.

A Government spokeswoman said Corrective Services Minister Fran Logan would return early from his holiday in London to deal with the situation and was expected to arrive tomorrow.

Geraldton resident Kate Woods, who lives in the outer suburb of Wandina, said people were on edge and there were "police everywhere".

"It makes you feel really uneasy, but the police presence was phenomenal," she said.

She said gates at her child's school had been locked and parents appeared to be keeping their children at home.

Prison was warned on understaffing: union

The WAPOU said the State Government was warned about "unsustainable" staffing at regional prisons during a scheduled meeting with the Justice Department before the breakout on Tuesday.

Mr Ledingham said understaffing was a statewide issue.

"They need to act now and they need to fund what is an overcrowded prison population statewide," he said.

"There are no savings to be made by reducing the number of prison officers in prisons across the state, because this is the outcome."

A 2017 report found Greenough Regional Prison was "old and worn out". ( ABC Mid West: Chris Lewis )

A Department of Justice spokesman said 284 prisoners were housed at Greenough prison on July 23, but there were beds for 333 prisoners.

However, Inspector of Custodial Services Neil Morgan said in a December 2016 report that Greenough was designed to hold just 223 prisoners, and the department's "reporting methods obscure the extent of crowding".

Another report by Mr Morgan at the start of 2017 found most prisoners at Greenough were sharing cells, eight of which housed six prisoners apiece.

That report found the prison to be "old and worn out", infested with mice and cockroaches and with facilities that were "simply too small for the prisoner population".

There have been ongoing concerns about overcrowding at Greenough. ( ABC News: Jade MacMillan )

It found relations between staff and inmates had fallen to such a low level, they were posing a security risk.

"The increase in prisoner numbers, the declining budget and the need to do more with less is creating pressures at the prison," Mr Morgan said.

There were more concerns about overcrowding at the prison last year when it was revealed some inmates were being forced to sleep on the floor.

Acting Opposition Leader Peter Collier said problems in the state's prison system were linked directly to the Government's efforts to rein in corrective services spending, calling for a new prison to reduce overcrowding.

"You cannot reduce the budget or the staffing of corrective services without the consequences and that is what happened," Mr Collier said.