Prison officials in Russia say the situation is under control at prison IK-7 in the Saratov region after hundreds of inmates rioted earlier on February 1.
The Federal Penitentiary Service (FSIN) said the riot was sparked after inmates refused to disperse when guards ordered them to break up a fight.
There were no reports of injuries or deaths.
The head of the regional FSIN branch, as well as prosecutors and the chairman of the regional public-oversight commission, quickly arrived at the prison, which houses particularly dangerous criminals.
The FSIN statement said there are about 800 inmates at the prison, but only a fraction of them were involved in the incident.
The FSIN statement did not elaborate on the methods used to restore order.
Conditions in the Russian penal system and allegations of violations of inmates' rights have come under scrutiny since a video surfaced in July showing at least 17 guards beating an inmate in a prison in the Yaroslavl region.
At least 15 guards from the Yaroslavl prison have been arrested following the public outcry following the release of the video.
