Six crews of firefighters were called to Norwich Prison after a fire broke out.
It is believed to have happened on a top floor of the prison.
Firefighters from Sprowston, Carrow, Earlham, Hethersett, Wroxham and Wymondham were sent to the scene, after being called at 5.33pm.
Some nearby residents reported seeing fire engines, paramedics and police rushing to the scene, and a smell of smoke hung around the permitter of the prison estate, although no damage was visible from the outside.
It is not believed that anyone was injured in the fire, and some police, fire and paramedics were seen driving away from the scene at 6.45pm.
Police said they were called to the incident, but were told 'everything is fine', and stood down.
One prison worker said the fire happened in a roof space, but he said he did not know the cause. He added that some staff had had to work longer shifts because of the fire.
Did you see what happened? Email martin.george@archant.co.uk
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