Twenty people have been charged as a result of a crack-down on illegal activity in Kaingaroa forest.
The joint operation between police and Timberlands was carried out over six days on three separate occasions last month and over the weekend.
The charges relate mainly to cannabis cultivation, theft and damage to machinery and also vehicle offences and some unlawful hunting.
A total of 45 people have also been issued with trespass notices.
Police say the forest is often used as a cover for criminal activities.
Timberlands says it has already noticed a drop in unlawful activity since the operation began.