A detector dog uncovered 11.5 grams of cannabis oil hidden in a pair of socks at Manawatu Prison.
Zena the dog found the drugs in a prisoner's incoming mail.
"This was a fantastic find by the team and shows that our efforts to prevent contraband from getting in to prisoners are working," says Acting Prison Director Graham Dack.
He said the socks and the drugs had been handed over to Police and they were continuing to co-operate with them in order to identify the sender and ensure they were held to account.
"Drugs and other contraband create a more dangerous environment for both staff and prisoners.
"Being effected by drugs prevents prisoners from fully engaging in the education, employment and rehabilitation programmes that can help them live a life free from crime when they are released.
"Stopping contraband from getting into prisons is a challenge that Corrections staff face daily."
Dack said it was disappointing to see people try to push boundaries in order to get drugs or other contraband to prisoners.
"We want people who try to introduce items into prisons to know that we will find them and they will face consequences."
Corrections staff conduct regular searches through incoming and outgoing mail, prison perimeters, cells and visitors.
