Up to 240 prisoners will be transferred out of HMP Birmingham after a 12-hour riot at the jail.

Nearly 600 inmates were believed to be involved in the disturbance at the privately run prison on Friday (16 December), after a warden was allegedly threatened with a syringe and had his keys stolen.

Staff then lost control of all four wings of the prison.

The Ministry of Justice confirmed control was regained at roughly 10.30pm after specialist riot squads from across the country were drafted in.

Truss confirmed on Saturday (17 December) there will now be a full investigation into the riot.

"I want to pay tribute to the bravery and dedication of the prison officers who resolved this disturbance," she said, reported the BBC.

"This was a serious situation and a thorough investigation will now be carried out.

"Violence in our prisons will not be tolerated and those responsible will face the full force of the law."

Mike Rolfe, national chairman of the Prison Officers Association, said the flare-up was not unexpected as more than 30 staff had left the prison, which is run by the controversial contractor G4S, in recent weeks.

"We've been warning for a long time about the crisis in prisons and what we are seeing at Birmingham is not unique to Birmingham, but it certainly would seem that this is the most recent worst incident since the 1990 Strangeways riot," he said.

He added that was "another stark warning to the Ministry of Justice that the service is in crisis".

During the disturbance, the BBC was contacted by several men claiming to be prisoners at the jail, who said poor conditions were behind the disturbance.

The men, who said they were calling from inside HMP Birmingham, cited inadequate staff numbers, poor healthcare and nutrition.

They said being on "lockdown" in their cells all day was a major factor that contributed to the trouble. It was the fourth riot at the prison in six weeks.

Truss's comments that inmates would "face the full force of the law" drew immediate criticism on social media for failing to tackle the heart of the problem.

On Twitter, Jane Turnball said: "Liz Truss says those responsible for prison riots will 'face the full force of the law'. Does that include G4S, MoJ and George Osborne?"

Michael Spurr, chief executive of UK prisons, said there was a problem of under-staffing, but also blamed the rise in psychoactive substances in prisons for the problems.

"We do need more staff in prisons," he said on Sky News. "I think that's true for Birmingham – it's true for a number of places. That's because over recent years, we have reduced the total number of staff working in prisons.

"We've closed 18 prisons, but the problems that prisons have had to face have increased. Effectively, what has happened is that we've got more prisoners who are more prone to serious violence – gang-related violence very often – and we've had a huge influx of illicit psychoactive drugs that have been pushed into prisons and those drugs have changed the dynamic in prisons.

He added: "It is the case that we need more staff to be able to manage the situation in prisons now. That's the funding that's been provided by the government that will provide that staff. And that will make a difference, but it is going to take some time to turn this around."

riot police
Prison officers in riot gear arrive at HMP Birmingham after inmates took control for 12 hours. Reuters