The Department of Corrections says it has thwarted an attempt by several prisoners to smuggle a stereo packed with cannabis into Rimutaka prison.
Assistant manager Richard Symonds says monitoring of phone calls by prisoners revealed the plan.
Mr Symonds says a prisoner tried to send a stereo to someone outside the prison.
Guards checked the stereo and discovered a letter inside it with detailed instructions to pack the stereo with cannabis and send it back to the prison.
