A cannabis haul worth $12.5 million has gone up in smoke as part of a police operation on the New South Wales north coast.

Since November, the NSW police cannabis eradication program has seized more than 6,000 plants found in dense bushland surrounding the Tweed, Richmond and Coffs Clarence districts.

Detective Superintendent Peter McErlain said aerial surveillance had been a key tactic in locating many of the hidden farms.

"We work very closely with aviation support branch, and PolAir is a great tool for us," he said.

"It can get us into very dense bushland we couldn't normally get into, and it plays a very significant role."

The multimillion dollar cannabis haul was today trucked to an undisclosed sawmill west of Bellingen, where the large plants were bunched and loaded onto a conveyor belt, then sent straight into an incinerator.

The only sign left afterwards was a large plume of cannabis smoke drifting into the skyline.

Police burnt the 6,000 plants seized in the operation. ( ABC Coffs Coast: Dom Vukovic )

Profits largely funding organised crime, police say

Superintendent McErlain said the quality and size of the plants seized were "a lot larger and healthier" compared to other regions in the state, largely due to the area's climate.

He said a large amount of the money from the crops was going straight into organised crime.

Superintendent McErlain said despite the ongoing police efforts to stop the illegal growing, there was a constant supply of perpetrators to replace those that were caught.

When asked why so many resources were being used to fight cannabis compared to other, harder drugs, he was unequivocal.

"Cannabis, there's a lot of debate about cannabis and the use of cannabis," he said.

"But at the end of the day it's a prohibited drug under the legislation of NSW, and we will be enforcing that legislation."

From March there will be additional resources added, with a newly formed Regional Enforcement Squad working across the north coast to break distribution networks for drugs, including cannabis and ice.