The director of Christchurch Men's Prison and two of his staff are on special leave as the Department of Corrections investigate "compliance with specific security procedures" at the facility.
The Herald understands that prison director John Roper was on his final employment warning before he went on leave.
Corrections would not comment on Roper or the other staff saying it was an employment matter.
Corrections Southern Region Commissioner Ben Clark announced the news to staff at the prison today.