Police found three shipping containers containing 370 mature cannabis plants and 70 seedlings and clones at a house near Whangarei last week.
An anonymous tip off to Crimestoppers led police to search the Whareora property, where they found two underground shipping containers, buried under a polyhouse, and an eight metre shipping container above ground, near a boundary fence.
They arrested a 45-year-old man, charging him with cultivation of cannabis.
They also searched another property owned by the man and found four unsecured firearms and some ammunition.
Police encourage people to call Crimestoppers if they have information on criminal activity and want to remain anonymous.
