Prison officials have dismissed reports of a "stand-off" between guards and inmates who reportedly took control of a wing on Friday.
They confirmed a “disturbance” had taken place, but called the suggestion of a stand-off between inmates and guards "speculation". There were no reports of any injuries.
The incident broke out at the HMP Northumberland, in Morpeth, at about 7.30pm on Friday.
Steve Gillan, general secretary of the Prison Officers Association, told the BBC that prisoners had taken control of an area.
“We do not know what has sparked this major incident, but I do know that 50 plus inmates have taken over a wing,” he said on Friday evening.
“We have teams from other establishments trained to deal with riots on their way. There is concerted indiscipline and our officers will try to contain it.”
The trouble broke out after prisoners refused to go back to their cells, the BBC said, while police were put on standby ready to assist.
A spokesman for Sodexo, which operates the prison, said the situation had been resolved.
He said: “We can confirm there was a disturbance at HMP Northumberland.
“It was confined to part of one wing of the prison and has now been resolved. We will carry out an investigation into this incident.”
HMP Northumberland houses around 1,350 inmates and is a category C prison, for inmates convicted of less serious crimes who cannot be trusted in open conditions but who are unlikely to make a determined attempt to escape.
Private firm Sodexo Justice Services took over the management of the prison in December last year.
Additional reporting by Press Association