Riot squads stormed a cell at Whitemoor Prison, March, after a prisoner took a hostage.

Details began to emerge today of the incident that happened a week ago after negotiators failed to bring an end to the nine hour siege. The hostage-taker flooded a cell and started fires.

The incident has been blamed by prison officers’ union officials on a shortage of staff: they claim some prisoners go unsupervised.

The incident at Whitemoor happened last Saturday at around 4.15pm when a prisoner entered another cell, took the inmate hostage, and refused all attempts to release him. The cell was flooded with water and according to reports “a series of small fires” were started.

In the early hours of Sunday, at around 1.15am, a decision was made to storm the cell using flash grenades. The victim was released. Neither inmate was injured although a prison officer is reported to have sustained a minor injury to his leg.

A spokesman for the Ministry of Justice said police were now investigating the incident at Whitemoor – one of two reported across the prison network the same weekend. The other was at HMP Garth in Lancashire.

The Guardian newspaper today quoted a spokesman for the Prison Officers Association as saying that “once again, we are seeing serious incidents which we believe are a result of staff cuts. These have resulted in a lack of purposeful activity and prisoners being unsupervised.

“Such incidents were costly and involve detailed investigations by the prison service and the police. These are the hidden costs of the cuts to the taxpayers.”

Whitemoor, that houses some 450 inmates, is a maximum security prison for men in Category A and B. It is one of eight High Security prisons. The prison focuses on settlement (helping those convicted of serious offences to make positive use of long sentences) and resettlement (reducing the risk of reoffending through assessment, work, education and offending behaviour programmes).

The prison includes a Dangerous and Severe Personality Disorder Unit. The Fens Unit is part of the national DSPD Programme of the Health Partnerships Directorate, providing thorough assessment and a fully worked out treatment model.

Whitemoor also houses a Close Supervision Centre. The unit prepares prisoners who pose a severe risk to others, to return to a normal prison environment.

• Were you working at Whitemoor last weekend? Or visiting a inmate? Phone or text 07918 691210 (in confidence) with information