Police and firefighters were put on alert after two serving prisoners climbed onto the roof of Dartmoor prison.
The prisoners gained access to the roof at around 2.10pm yesterday where they remained for a number of hours.
A Prison Service spokesman confirmed the two prisoners had climbed onto the roof of the jail. The spokesman said specialist staff had worked to "bring the situation to a safe conclusion".
Police said they were contacted by prison authorities at 2.38pm, making them aware of the situation, while the Devon and Somerset Fire Service were also alerted, in case of need of the service's aerial platform, based at Crownhill in Plymouth.
HMP Dartmoor houses 640 prisoners and was built in 1809. It was recently criticised by HM Inspectorate of Prisons following a review. While improvements were noted, its wings and cells were considered to be still "shabby", "cold and damp".
Following a damning inspection in 2010, the latest report earlier this year revealed progress in terms of being safer, pro-active and "reasonably effective in addressing the number of violent or antisocial incidents."