A riot is understood to have taken place at HMP Bedford on Sunday.
Five members of staff are believed to have been hospitalised during the incident, which took place at midday.
One insider, who asked not to be named, said: “The senior staff, at the prison and Beds Police alike, do not want this declared a riot officially.
“However, as the control over the majority of the prison was completely lost until Tornado units (specially trained prison riot police) arrived and entered to regain control, a riot is exactly what it was.
“Beds and Herts Police were asked to have all PSU officers (riot trained officers for public order generally outside of prisons) that were on duty, be made available for HMP Bedford. All of those officers were not allowed to go off shift/go home at their due finish time, whilst attempts were made by tornado units to gain control.”
This follows the strike at Bedford Prison which began on Friday morning.
Staff told the Times & Citizen that they fear it is only a matter of time before someone dies on duty because of repeated cuts to staff and resources.
Around 130 staff at HMP Prison at Bedford are currently on strike but they have been threatened with legal action by the prison governor.
The insider added: “The senior officials/officers in dealing with this and many incidents at this prison, are hellbound on keeping the real issues from the media and public.
“As the transparent truth threatens their position, career and pension prospects.”
Mark Fairhurst, national chairman of the Prison Officers Association (POA), said: “The POA are appalled that members concerns and rights to work in a violent free workplace have once again been ignored.
“We fully expect the prisons minister Rory Stewart, who we have a positive relationship with, insists that Her Majesty’s Prison and Probation Service directors listen to the POA and immediately act to address our members’ concerns and begin to make our prisons safe for staff and prisoners.”