A Corrections officer at the Otago Corrections Facility (OCF) has been sacked for serious misconduct.
Prison management said no police charges would be laid and have declined to reveal the reasons for the dismissal.
Inquiries by the Otago Daily Times have revealed OCF management became aware of an issue surrounding the officer last month and when all the facts were presented, the officer was instantly dismissed.
Details of the officer and the offending are not being released by OCF or the Department of Corrections, both citing privacy reasons.
It is not known if the officer is male or female, how long they had worked as a corrections officer at Milburn or any other prison, whether he or she has any previous blights on their personal file or the exact nature of the offending.
OCF manager Jack Harrison said the officer would not face police charges as no criminal activity was involved.
The officer is the only OCF staff member to be dismissed for disciplinary reasons since the 335-bed facility was officially opened a year ago.
Serious misconduct breached the department's code of conduct, which gave prison bosses the power to instantly dismiss staff.
This was what had happened in the OCF matter, Mr Harrison said.
"The department demands a high level of integrity from staff and the vast majority of them do an excellent job in an often volatile environment.
"The actions of one staff member should not detract from the hard work, dedication and professionalism shown by staff at OCF," Mr Harrison said.
The department's website contains examples of offences which constitute serious misconduct.
These can include violence or threats of violence against prisoners and others in the workplace, threatening, abusive or insulting behaviour to anyone in the workplace, failing to comply with the department's safety policies and procedures and having an inappropriate relationship with a prisoner.
Corrections Association New Zealand president Bevan Hanlon could not be reached for comment yesterday.