A man is “throwing slabs” at police officers from the roof of HMP Barlinnie.
Staff are currently trying to control the incident.
The man is believed to be a current inmate at the prison in Glasgow.
The supposed inmate is understood to be throwing roof tiles at officers below.
Visits to the hospital have been cancelled due to the ongoing situation, it is understood.
A Scottish Prison Service spokesperson said: “I can confirm an incident is ongoing, and staff are working to bring it under control in a way that safeguards the wellbeing of all concerned.”
It has been reported that the man is throwing slabs at officers as a form of protest over the lack of support in the prison.
It is thought he made his way onto the top of the building on Sunday morning.
The man is understood to be in an agitated mood.
The Scottish Prison Service (SPS) confirmed that the incident is ongoing.
Police Scotland confirmed the incident had not been reported to them.
Last week, it was revealed Prison bosses at HMP Dartmoor are spending almost £10,000 on teaching inmates to click their fingers and stomp their feet alongside music.
The “body percussion” programme is designed to help prisoners manage their anger.
According to The Sun, inmates are encouraged to use different parts of their bodies to make noise alongside pop music.
A year-long contract was given to Wiltshire-based firm Kaboom! to run the musical workshops in the prison.
The deal cost £9,600, according to the Ministry of Justice (MOJ).