The Department of Corrections has stood down five of its Rimutaka Prison staff following allegations of misconduct.
The staff have been placed on special leave from today and employment investigations are underway.
Police have been making enquiries into the prison in Upper Hutt since 2020 and have passed on information to Corrections which identified 10 staff, including management, whose alleged actions were of concern.
Of the 10, one has already resigned and five are on special leave while they are being investigated.
Corrections said the remaining four would be spoken to by senior management shortly, but two of this group were not at work as they were subject to other employment investigations.
The allegations included introducing contraband including phones and food, workplace bullying, failure to follow procedures critical to the safety and security of the prison, failure to maintain professional boundaries and inappropriately accessing prisoner information.
Corrections chief custodial officer Neil Beales said: "We will not tolerate this type of behaviour in our prisons. We expect a high standard of conduct from all employees.
"The nature of our work means we must act beyond reproach at all times."
In his statement, Beales pointed out that Corrections employed 10,000 staff nationwide and the majority acted "integrity, honesty and professionalism".
"If any staff don't meet the standards required, we take action."
He said staff at Rimutaka Prison were focused on improving its culture, ensuring professional standards of behaviour were maintained and that the management of inmates was being done to high standards.