Dozens of prisoners have been relocated after more than 200 rioted at HMP Bedford and took control of two wings of the prison.
Hundreds of prisoners got out of their cells and caused chaos on communal passageways at the prison around 17:00 GMT on Sunday.
The Prison Officers Association (PSO) said 230 inmates left their cells, stole guards’ keys, broke into medical supply areas, and took control of two wings of the prison.
Mobile phone footage from inside the prison has been published online, which shows prisoners in control of the gangways, shouuting, and chanting.
Police and prison officers from around the country were called to the Category B prison to bring the situation under control after reports of loud bangs and prisoners starting fires.
The incident lasted about six hours, and the prison said no staff members were hurt in the incident, but two inmates were treated for minor injuries.
The motive for the riot is unclear, but in a recent report on the prison, inmates claimed that it was difficult to get hold of clean clothes or bedding. Illegal drugs are also reportedly widely available and “easy” to access at the prison, with the number of inmates who said they had developed a drug problem while at HMP Bedford more than tripling from four percent to 14 percent between 2014 and 2016.