Disorder has broken out at a prison for the second time in a week.
Serco, which runs HMP Lowdham Grange in Nottinghamshire, said there was an "incident of concerted indiscipline" late on Tuesday.
Violence broke out on 26 July with reports stun grenades had to be used to restore the situation.
The latest outbreak was "peacefully resolved" and involved only a small number of prisoners, Serco said.
A spokesperson added: "No staff or prisoners were injured and it did not affect any other parts of the prison.
"There was an incident of concerted indiscipline by a small group of six prisoners on one of the wings late yesterday evening, which was peaceably resolved."
'Violence and fear'
A sister of one inmate said last week's trouble was prompted by conditions inside the jail and prisoners "were chucking things all over the place".
Serco insisted this unrest involved only six prisoners.
Lowdham Grange is a Category B men's prison, which houses 888 prisoners.
A 2015 report by HM Inspector of Prisons found "high levels of violence against staff and prisoners".
Commenting on the prison system as a whole, a spokesman for the Prison Reform Trust said: "Safety indicators are setting records for all the wrong reasons.
"Record levels of self-harming, record levels of assaults on prisoners and record levels of assaults on staff show that violence and fear is the daily reality for many people in prison."