Staff at Christchurch Men's Prison have caught a visitor bringing in a large quantity of narcotics, the Corrections Department says.
Acting prison manager Trevor Saunders says the woman appeared to be under the influence of drugs or alcohol and staff became suspicious - particularly when she asked to visit a female prisoner.
Mr Saunders says the woman's vehicle was searched by a drug dog handler and a large amount of drugs was discovered.
The woman is facing charges.