Police have arrested eight men and three women and seized a haul of illicit drugs that could cause an estimated billion dollars worth of harm to the community.
Those arrested in raids by police named Operation Skipjack "phase 2" are aged between 25 and 44. Four people were previously charged in relation to "phase 1", taking the total number of arrests to 15.
Led by Wellington Police District Drugs and Organised Crime Unit, over the past two weeks more than 70 Police and Customs staff have executed 22 search warrants in Wellington, Hutt Valley, Kapiti Mana, Horowhenua and Palmerston North.
The haul included class B controlled drug Gamma Butyrolactone (GBL), and class C controlled drug Eutylone, during "phase 2" of Operation Skipjack.
During phase 1 of the operations last November, an investigation was launched into alleged offending by a local drug-dealing syndicate importing and distributing controlled drugs known by the street names of G, liquid ecstasy, and rinse.
"As the Operation moved into 'phase 2' this year, police, along with our Customs partners, identified further alleged importations by the syndicate which had changed its methods and was now importing quantities through the mail system," Wellington District Field Crime Manager, Organised Crime, Detective Inspector Darrin Thomson said.
"Due to the diligence of NZ Customs, more than 20 parcels were intercepted and stopped from arriving at the intended location."
More than 7000 litres of GBL are imported in New Zealand from countries that include the Netherlands, United States, Spain and China, with NZ Customs seizing significant amounts of the drug during the investigation.
Police said it would be working with international counterparts on prevention and enforcement.
The New Zealand Drug Harm Index identifies the community harm of these drugs at more than a billion dollars and the street value of the GBL involved is estimated at $28 million.
"Operation Skipjack will cause significant disruption in the illicit drug market and the seizure of such an enormous quantity of GBL will certainly reduce and prevent the harm associated with this drug," Thomson said.
"Accompanied with the 'high alert' drug warning system that was activated in November identifying this issue, Operation Skipjack has significantly impacted this syndicate's activity and the associated harm peddled into our communities."
Over the two phases, a total of 50 charges have been filed.
During the searches, police also seized $60,000 cash and three firearms, including a semi-automatic weapon with 70 rounds of ammunition and a kilo of methamphetamine.