Personnel from the New Zealand Defence Force and New Zealand Police scan the bush for cannabis plants from anNH90 helicopter.

About 10,000 cannabis plants have been seized as part of an annual police operation supported by the New Zealand Defence Force (NZDF).

Thirty firearms and more than $50,000 in cash were also confiscated during the operation.

At a single West Coast property, 500 cannabis plants and 1.3 kilograms of dried head and leaf were found.

Detective Senior Sergeant Scott McGill said 68 per cent of the cannabis plants that were seized and destroyed came from the Tasman region.

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The operation, which was supported by NH90 helicopters and crew from the Royal New Zealand Air Force's No.3 Squadron, was carried out in February and March.

It covered Nelson, Marlborough and the West Coast in the South Island and Manawatu, Horowhenua, Whanganui, Ruapehu and Taranaki in the North Island.

NZDF Personnel from the New Zealand Defence Force and New Zealand Police scan the bush for cannabis plants from an NH90 helicopter.

"The areas where they are cultivating cannabis are remote and so the NZDF's air support is vital," he said.

"It has dealt a blow to those engaged in these illegal activities. But more importantly, about 10,000 cannabis plants have been destroyed and will no longer be marketed in our communities, especially to our young people."

Police conduct cannabis recovery operations are carried out annually.