A drug researcher is warning more fentanyl will arrive in New Zealand.
The Government's working to tighten controls on 23 substances - helping to allow a police and Customs crackdown.
Health Minister Simeon Brown want to categorise three drugs similar to fentanyl as Class A substances, with harsher penalties for manufacture.
Massey University's Chris Wilkins says fentanyl is a cheaper alternative for many drugs.
"They've been replacing heroin with fentanyl - but now, increasingly, a whole lot of other drugs. And given that economic incentive, it's hard to see that New Zealand is going to avoid this problem."
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