Seven people have been arrested for allegedly smuggling over 100kg of methamphetamine into New Zealand disguised as concrete.

Six men and one woman, aged between 36 - 65 years, are facing charges for the importation and possession for supply of a Class A controlled drug after Customs officials discovered the drugs in a 1.4 tonne shipment from China.

The consignment was declared as "outdoor leisure products", including swings, slides, a furniture set, and garden lights - but after extensive examination officials found a mix of methamphetamine and gypsum hidden in 16 concrete outdoor umbrella stands.

Customs Investigations manager Bruce Berry said superb targeting and inspections work led to the discovery of this new way to disguise meth, and the investigation has exposed how some syndicates operate.

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The extracted methamphetamine's purity is yet to be finalised, but is estimated to be at least 100-120kg with a street value of around $100-120 million. Photo / Supplied
The extracted methamphetamine's purity is yet to be finalised, but is estimated to be at least 100-120kg with a street value of around $100-120 million. Photo / Supplied

"This type of concealment is difficult to detect, and the combination of good investigative trade craft informed by effective analysis by ESR directly led to this result," he said.

"The syndicate was operating in a very 'compartmentalised' way - using different groups of people to receive the meth, extract it, and then have it ready for pickup in an effort to defeat any law enforcement response.

"Transnational criminal syndicates are finding more sophisticated ways to operate and disguise drugs, but Customs and our partners the Police are alert to this, continually developing new techniques and technologies to target and stop them."

The extracted methamphetamine's purity is yet to be finalised, but is estimated to be between 100-120kg with a street value of around $100-120 million.

Based on the NZ Drug Harm Index, this amount has avoided a potential social and community harm cost of between $124-148 million.

The shipment was linked to a company believed to have been set up solely to smuggle drugs.

A subsequent joint investigation led to several search warrants being carried out in Auckland in the past week, where further evidence linking those arrested was found.

The charges faced carry a maximum penalty of life imprisonment.

Detective Superintendent Greg Williams from the Police National Organised Crime Group said Customs and Police worked closely together to monitoring the movements of the container and activity around it.

"This is a significant seizure which would have had the street value of many millions of dollars while causing an equal amount of social harm," he said.

"We will continue to target and catch those responsible for attempting to profit from this type of transnational organised crime."