11 Vietnamese nationals have been deported after Police busted a major cannabis-growing operation in Auckland

Police made the arrests after targeting 30 properties in the city last week believed to be involved in an organised crime group.

They say they destroyed three-thousand cannabis plants and 48 kilograms of dried cannabis - altogether valued at 18-million dollars

Acting Detective Inspector Greg Brand says the gangs modify residential properties to grow the plants - creating a significant fire risk.

He says the majority of those arrested were in New Zealand illegally and are now back in Vietnam.