Staff assaulted and 'multiple' fires at HMP Featherstone
Inmates at a West Midlands prison have assaulted staff and started "multiple" fires in a week-long outbreak of disorder.
A major incident was declared at Featherstone Prison on Thursday, the Prison Office Association (POA) said.
Riot staff were drafted in to deal with the trouble, which also included a hostage situation.
The Ministry of Justice (MoJ) said any prisoners involved could face disciplinary action.
An extra 20 staff have now been called in to maintain order at the category C prison near Wolverhampton, the POA said.
An inmate at the jail, which holds more than 600 prisoners, contacted the BBC on Thursday and said the disorder started following a fight in one of the prisoner accommodation blocks.
The fight could not be brought under control and officers had to call in reinforcements.
He claimed three people were taken to hospital on Tuesday after further trouble, and prison staff were assaulted on Wednesday when they attempted to move some inmates were to another block.
Prisoners set fire to cells on Thursday and Staffordshire Fire and Rescue Service sent two crews to the jail but have not released any more details.
The POA said a specialist team was drafted in to deal with the hostage situation and disturbances which has now been stood down.
The union said its members are facing increasing levels of violence, with assaults rising by 40% in the last year.
In a statement, it said "it will do everything it can to protect the safety of our members and prevent them from being used as punch bags on a daily basis."
"We need to flood our prisons with staff to ensure stability and safety. The chronic staff shortages brought about by savage budget cuts and failures by the employer will no longer be tolerated," it added.
The MoJ said safety in prisons was "fundamental to the proper functioning of the justice system" and a vital part of reform plans.