Four people are facing charges relating to methamphetamine after a large cargo of t-boc methamphetamine was stopped at the border.

It's alleged that a cargo consignment labelled as dishwashing liquid and containing an estimated 160 litres of t-boc methamphetamine was imported from Hong Kong on 28 January 2017.

This is a form of methamphetamine which is chemically masked to prevent it being detected.

The accused are facing a range of offences relating to the supply of methamphetamine and the possession of equipment with intent to manufacture a controlled drug (methamphetamine).

This follows a New Zealand Police and New Zealand Customs Service operation which led to search warrants being executed last night at residential and commercial addresses in Lynfield, Waitakere, Newmarket, Epsom, Avondale and New Lynn.

It is alleged that a cargo consignment labelled as dishwashing liquid and containing an estimated 160 litres of t-boc methamphetamine was imported from Hong Kong on 28 January 2017.

Methamphetamine was concealed in dishwashing liquid containers.

Through a chemical process, t-boc methamphetamine can then be converted back to methamphetamine for the purpose of supply. It is believed to be the first time that this form of methamphetamine has been seized in New Zealand.

The liquid and equipment seized in the operation is believed to have the capability to convert the t-boc methamphetamine into about 120kg of methamphetamine.

Removing this quantity of methamphetamine from the supply chain equates to reducing the drug harm that would have otherwise been caused to the community by $148m, says Detective Superintendent Dave Lynch.

He says the joint investigation is a very good example of cooperation between New Zealand agencies and overseas partners to disrupt the supply chain of methamphetamine.

'The approach to disrupting the supply chain hinges on the strong networks we have built with our partners in the Chinese National Narcotics Control Commission, across Government including the New Zealand Customs Service.

'With these strong networks, Police and Customs are becoming increasingly successful at disrupting the supply of illicit drugs into this country and holding those who profit from importation to account.

'We believe this is the first time a consignment of t-boc methamphetamine has been intercepted in New Zealand, and we rely on our strong partnerships both at home and overseas to stay abreast of the changing trends in the illicit trade in drugs.” says Mr Lynch.

Customs Investigations Manager Maurice O'Brien says the success of this investigation shows that criminal syndicates may to great lengths and are becoming more sophisticated in their methods of concealment, but this is not beyond the detection of law enforcement authorities.

'Customs has the mechanisms and technology in place to identify and intercept such shipments. We will continue to work alongside Police and our overseas partners to target and stop drugs at the border, in order to prevent it from getting into and harming our communities.”

Four males aged 59, 47, 38 and 54 are due to appear in the Auckland District Court today and the investigation is ongoing.