Garage methamphetamine lab uncovered in Kaikohe

A man tried to smash up a suspected methamphetamine laboratory after police stumbled across the operation, police say.

Kaikohe police Senior Sergeant Chris Scahill said police visited a property at Okaihau, about 13km north-west of Kaikohe. They were there on an "unrelated matter" when they realised there appeared to be a methamphetamine laboratory in a garage.

One man barricaded himself inside the garage and smashed up equipment, spilling what was believed to be chemicals. Three police officers were treated by a St John ambulance officer at the scene after suffering mild side effects.