Police have found drugs in plastic bags used by a criminal group to provide sandwiches to school children.
The Waikato police have arrested 30 people in a region-wide operation targeting organised crime.
Those arrested face a total of 87 charges relating to dealing methamphetamine and cannabis, possessing firearms and stolen property.
Members from various gangs were among those arrested, Detective Sergeant Kristine Clarke said.
"This operation established a very clear link between gangs and the distribution and sale of methamphetamine and cannabis," Ms Clarke said.
At one property the police seized 80 tinnies packaged in the same plastic bags used by the group to provide sandwiches to school children.
"Also of particular concern was a property located next to a kindergarten where drugs were being dealt, gang regalia was displayed and an illegal shotgun was located," she said.
In many cases children were living in houses where drugs were being sold, the police said.
Three illegal firearms were also found during the search.
The offenders have been appearing at the Hamilton District Court over the past week.