$50 million of methamphetamine hidden in an air shipment from Mexico has been seized by police in Christchurch.

Police say more arrests are likely after they seized $50 million of methamphetamine destined for the streets of Christchurch.

The South Island's largest haul of the drug came when a 49-kilogram shipment was discovered in 40 packages hidden among a cargo of safety lights on November 1.

The two-week operation ended on Tuesday night with armed raids of several properties in Christchurch and Auckland.

Two Christchurch men, aged 25 and 31, appeared in the Christchurch District Court on Wednesday charged with importing a class A drug and possession of methamphetamine for supply.

READ MORE:

* Methamphetamine supply and use continue to grow

* Meth 'hail storm' destined for Christchurch

* Big spike in bill for ridding state houses of meth in just one year

Both men were granted interim name suppression and remanded in custody until November 20, when they would appear in court by video-link.

Canterbury district crime manager Detective Inspector Corrie Parnell said the drugs were brought into Christchurch from Mexico in packages weighing between 1kg and 1.2kg. The drugs had a potential street value of $50m and the seizure prevented $60m worth of additional community harm, he said.

Police believed much of the drug was "destined to end up on the streets of Christchurch", but they did not let the freight reach its destination.

Parnell said the investigation was still "in its infancy", with further arrests likely.

"We have significant inquiries ahead of us in terms of both Customs, police and other government agencies."

He said the seizure was a "significant result".

"Our team has worked relentlessly over the last fortnight to bring this operation to the state it's in today.

"These drugs, should they have made it to the streets, would have caused significant harm to people and communities, not just in Canterbury, but across the country."

Methamphetamine wrecked lives, broke down families and negatively impacted the community, he said.

"It takes enforcement and a whole-of-Government approach, along with education to reduce demand and victimisation caused by this drug."

Customs manager Joe Cannon said the methods people were using to bring drugs into the country were "constantly evolving".

"There's always an incentive to bring this product into the country because of the price it fetches.

"This seizure was the result of risk-profiling and targeting work that Customs carries out for all goods, people and craft coming into New Zealand – whatever the region or method of import."