A fire was started at HMP Ranby during an ongoing disturbance which saw 120 inmates refused to return to their cells, The Prison Officers' Association (POA) said.
A spokesman for the Prison Service said minor damage was sustained and there were no injuries to staff or prisoners.
More top news
A dull and wet start with some sunshine in south-east Scotland and north-east England.
In a rallying call at the Democratic National Convention, the former US president said Hillary is 'the best darn change-maker I ever met'.