Eight men are facing charges following police raids across multiple North Island centres.
Search warrants were carried out in Hamilton, Palmerston North and Ngāruawāhia - a small town north of Hamilton - over the last couple of weeks, said Detective Inspector Graham Pitkethley.
They led to the arrest on Thursday of eight men aged between 20 and 50, facing several charges including participating in an organised criminal group, unlawful possession of firearms and drug-related supply and possession charges.
"Firearms, cash, drugs, stolen property and motor vehicles were seized during the search warrants," Pitkethley said.
It was the climax of a four-month investigation, Operation Mikado, into the "large-scale distribution of methamphetamine, cocaine, ecstasy, MDMA and cannabis". The group supplied drugs across the mid North Island, police said.
"Unfortunately, during the investigation and subsequent search warrants we became aware that there were a number of children who have been exposed to drug dealing and illegal firearms," Pitkethley said.
"This is extremely concerning, particularly because it puts them in a vulnerable position and could negatively influence their behaviour."
Police said drugs, particularly meth, remain a lucrative business for organised crime.