The British government was urged to address the issue of prison overcrowding after specialist officers were called to deal with a disturbance at a jail.
Specialist prison officers were called to HMP Ashwell, near Oakham, Rutland, to deal with an incident of "concerted indiscipline", the Ministry of Justice said.
The prison's perimeter was secured and the surrounding area cordoned off for much of the early part of today as inmates were taken out in several prison vans - all with loud banging coming from inside.
It is believed prisoners had set fire to some areas inside the low-category C institution, as plumes of smoke were seen rising. Fire engines, police riot vans, and an ambulance could be seen near the front entrance of the prison.
The disturbance has prompted calls for the Government to take action on the growing crisis of prison overcrowding from both politicians and prison officers. But the Ministry of Justice denied HMP Ashwell was overcrowded.
A spokesman for the Prison Officers Association said it was believed all 400 prisoners were engaged in acts of indiscipline and the police had surrounded the prison to protect the public.
Leaders of the POA said they were not surprised to hear of the disturbance. National chairman Colin Moses said: "We have been warning of this type of disturbance for many months, but no one wants to listen."