A series of nationwide raids by police have seized a large quantity of psychoactive drugs, including more than 10kg of synthetic cannabis.
The psychoactive substances found by police could have been used to manufacture 150kg of synthetic cannabis - worth a street value of $1.5 million.
Acting Detective Inspector Roger Small, of Waitemata Police, said the raids were part of Operation Tiger.
Details of Operation Tiger were revealed last weekend by the Herald on Sunday.
Last year, police began receiving tip-offs from criminal sources and Customs officials about an increase in suspicious drug-loaded packages coming through the international mail system.
An extensive operation discovered Auckland teens were importing drugs online and selling it to their peers.
During the six-month operation 13 people were arrested, with 12 having since appeared before the Auckland, Waitakere and North Shore District Courts.
Small said Waitemata Police, alongside units in Palmerston North and Christchurch, executed search warrants at nine addresses this morning searching for psychoactive substances.
The warrants were executed in the Auckland suburbs of Henderson, Glendene and Red Beach, with further warrants taking place in Clarkville, North Canterbury and in the Christchurch suburbs of Hornby and St Albans.
Two more search warrants were also executed in Palmerston North.
Police also located four firearms during today's searches.
The raids followed an investigation which began in June and centred on the interception by Customs of more than a kilogram of AMB-Fubinaca and AB-Pinaca - the psychoactive substances used in the manufacture of synthetic cannabis.
The operation also follows further search warrants by Waitemata Police in Rodney last week where 2kg of AMB-Fubinaca and 11kg of synthetic cannabis was seized.
The 3kg of AMB-Fubinaca and AB-Pinaca seized during the raids would be sufficient to manufacture 150kg of synthetic cannabis.
A 48-year-old man from Glendene was arrested in the raids.
He will be appearing in the Waitakere District Court on charges relating to possession of a firearm and ammunition as well as possession of a class A drug.
Police are also waiting for the test results from samples of the psychoactive substances seized, which have been sent for analysis.
Police anticipate further charges will be laid as investigations continue.
"We will do everything we can to hold those responsible for manufacturing psychoactive substances to account," Small said.
"This is only the tipping point and police are continuing to conduct enquiries around psychoactive substances. We are confident that further arrests will come as we continue to investigate this serious issue."
Customs intelligence manager Wei-Jiat Tan said seizures made at the border were a good indication of new and emerging drugs, and Customs shared this with its partners to disrupt production and supply across New Zealand.
"Chemical properties of psychoactive drugs are ever evolving and potentially lethal - especially if amateurs are producing them.
"These drugs can be life-threatening for users, who have no way of knowing what they're really taking. It's not worth the risk," Tan said.