A report by Criminal Justice Inspection and Her Majesty’s Inspector of Prisons in England and Wales in November has described Maghaberry jail as unstable and unsafe.
Inspectors announced that they would go back to the prison this month to check on progress.
Around 20 inspectors plan to assess what improvements have been made.
It is expected they will spend two weeks on their assessment, and publish their findings before May.
The report published in November was the most critical ever about a prison in Northern Ireland.
Nick Hardwick, Her Majesty’s Chief Inspector of Prisons, said the jail was ‘the most dangerous’ he had ever visited.
The prison houses men serving long sentences for serious offences as well as suspects who have been remanded in custody before trial.
Brendan McGuigan, of Criminal Justice Inspection, said he was concerned that if the issues identified were not addressed as a matter of urgency, there could be ‘serious disorder or loss of life.’
Stormont’s Justice Minister David Ford and the Director General of the Northern Ireland Prison Service, Sue McAllister, were shocked by the level of criticism.
The follow-up inspection starts on Monday morning, as inspectors from Criminal Justice Inspection and Her Majesty’s Inspectorate of Prisons return to the site.
They are being joined by members of the independent health watchdog the Regulation and Quality Improvement Authority (RQIA) and the Education and Training Inspectorate.
The inspection report published recently was so bad there is an expectation that things can only get better.
The Department of Justice and the Northern Ireland Prison Service insisted that was the case and said there had been improvements in Maghaberry since the last time the inspectors paid a visit.