HMP Birmingham riot repairs 'will cost £2m'
The cost to repair damage caused by a riot at HMP Birmingham will be in the region of £2m, the BBC understands.
All the locks will be replaced at the prison following Friday's disturbances.
A bunch of keys taken from a prison officer as the trouble began was recovered but officials remain concerned about the risk of copies being made.
Justice Secretary Liz Truss has said G4S, the private firm which operates the jail, will cover the costs.
Prisons Minister Sam Gyimah visited the prison on Wednesday and met staff who were on duty at the time of the 12-hour riot.
Stairwells were set on fire and paper records destroyed during the trouble in four wings of the category B prison.
More than 460 prisoners have been moved out of the prison since the riot.
The disorder came months after a report by the Independent Monitoring Board said staff were concerned inmates were taking substances which can make them violent.
Asked how substances were getting into the prison, Jerry Petherick, managing director of custodial and detention services at G4S, said "a very small minority of staff are corrupt".
He also told BBC WM on Wednesday that contraband was also being thrown over prison walls, taken in by visitors and drones were being used.
Meanwhile, Lord Ramsbotham, a former chief inspector of prisons, said the riot should be investigated by an independent and outside observer.
The Crossbench peer questioned if the Government would bring in someone to examine the disorder.
Ms Truss announced earlier this week that Sarah Payne, adviser to the independent chief inspector of probation and former director of the Welsh prison service, would lead the investigation.