A search of an inmate's cell at Waikeria Prison in March uncovered a collection of extra bedsheets, with which it is thought the prisoner was planning to scale the fence.
The Corrections Department says a potential escape from the Nikau unit of Waikeria Prison near Te Awamutu was foiled in March.
Concerns were raised after the prisoner got a thumb stuck inside the cast on his arm, in an apparent attempt to be escorted to a medical centre.
Prison manager Kevin Smith says reservations about the prisoner's unusual behaviour ultimately resulted in the search of the cell.
The prisoner has since had his security classification reviewed and has been relocated to a medium security unit.
Waikeria Prison can accommodate more than 1000 remand and serving prisoners in security settings ranging from minimum to high-medium.