Sue McAllister of the NI Prison Service
Attacks on prison officers in Northern Ireland have doubled in the last three years.
The Prison Officer's Association told UTV News that injuries from the attacks ranged from bruises to broken bones.
Finlay Spratt of the POA said: "Sick levels have fairly increased over this past number of years and we believe it is all down to the amount of pressures on prison officers because of the lack of staff."
It was also revealed that at the Young Offenders Centre at Hydebank in South Belfast, a prison officer was knocked unconcious before being dragged into a cell.
It was only for the fact another prison officer was able to intervene that the officer wasn't harmed further.
According to the POA, attacks are now happening at an average rate of one per day.
Up until July of this year alone, there were 248 attacks on officers, compared to 327 for all of last year.
The head of the Prison Service in Northern Ireland, Sue McAllister, told UTV: "What it shows is that we look after some people with some very challenging behaviours.
"Our staff do a very difficult job and they do it very, very well.
"Prisons are inherently challenging places. There is always a risk to our staff presented by some of the people that we look after."
Mrs McAllister continued, saying that she was taking the current staffing and overcrowding situation very seriously.
She said: "We don't tolerate violence against anybody in our prisons - particularly our prison officers who work on the front line on a daily basis.
"What we have been able to do is reduce the amount of overcrowding by opening up new accommodation and reopening unused accommodation so that crowding levels have reduced and that means that our staff are safer."