Otago Corrections Facility general manager Dave Miller said three prisoners in the unit assaulted staff on three consecutive days last week.
Punches were thrown during two of the alleged assaults and as a result in both of those incidents, the prisoners were relocated and the matter referred to police.
"The prison is carrying out daily reviews of tension in the unit, and this will continue until it’s assessed it is no longer required.
"Additional staff and support were in place in the unit until today, and will be immediately reinstated if it is determined they are required, Mr Miller said yesterday.
"The reality is the threat of violence is something we cannot eliminate entirely, but we are committed to doing everything possible to minimise this risk and provide the safest environment possible for staff and prisoners."
Assaults on staff were "unacceptable", Mr Miller said.
"Violence in prison is not tolerated and anyone who resorts to this behaviour will be held to account."
On Monday last week, a prisoner punched a staff member in the face, he said.
The prisoner was relocated and the incident was referred to police for consideration of criminal prosecution.
The following day, a prisoner did not follow instructions and pushed a staff member in the chest.
That prisoner was charged with misconduct, Mr Miller said.
Then, on Wednesday, a prisoner punched a staff member in the head, Mr Miller said.
The prisoner was relocated and the incident was referred to police for consideration of criminal prosecution.
In each case, staff responded immediately to assist their colleagues and secure the prisoner.
One staff member was seen by their general practitioner (GP) as a precautionary measure. No other staff required off-site medical treatment.
All staff were back at work and were being fully supported by managers and the corrections facility welfare team.
"There is no evidence to suggest these assaults are linked, and each incident involved a different prisoner," Mr Miller said.
Training and tools were in place to keep staff safe.
This included training in de-escalation techniques and interpersonal and tactical communication skills, through to stab-resistant vests, body cameras, and pepper spray, Mr Miller said.
"We are continuing to work with the unions to implement our Reducing Violence and Aggression Joint Action Plan, and developing the next phase of this plan, called ‘Safer Prisons’, to ensure we are adapting and responsive to the current challenges and risks of the prison environment," he said.
In July, after a series of assaults against staff at the prison were linked to street gangs, a source told the Otago Daily Times the assaults had left staff at the prison fearing for their safety.
A source yesterday said staffing was a serious issue at the prison.