Police are investigating claims that drug users are turning to "home bake" heroin in response to the tight control of the drug trade by criminal gangs.
The substance is created when morphine sulphate tablets or codeine-based pills are converted into heroin.
The head of the Auckland Drug and Organised Crime Squad, Detective Senior Sergeant Chris Cahill, says drug traders and police informants have suggested gang involvement in the methamphetamine trade has driven addicts to produce their own heroin.
He says the production of home bake heroin is at a much smaller scale than P production, so its prevalence is harder to judge.
Detective Senior Sergeant Cahill says heroin use is still very minor in New Zealand.