Staff were attacked with pool balls during a disturbance at a high-security prison, the BBC understands.
Up to 80 inmates at HMP Long Lartin in Worcestershire became violent, forcing staff to retreat, a source said.
BBC home affairs correspondent Danny Shaw said he understood about 10 “Tornado teams” of riot officers were sent to the prison on Wednesday.
The Prison Service said the incident had been “successfully resolved” by Thursday morning.
No staff or inmates were injured, it said.
“We do not tolerate violence in our prisons, and are clear that those responsible will be referred to the police and could spend longer behind bars,” it added.
Our correspondent said there had previously been serious violence in local and training prisons, but to have a disturbance like this at a high-security jail would cause alarm at the MoJ.
He said the staff on E wing had retreated and it had been secured so the troublemakers could not go elsewhere.
There were also reports of a separate protest elsewhere in the jail, our correspondent said.
The disturbance followed riots at a number of jails in recent years, including Lewes, Bedford, Birmingham and Swaleside.