Police are investigating to determine the source of powdered fentanyl after 12 people were hospitalised in Wairarapa over 48 hours following the drug being sold as methamphetamine or cocaine.
This is the first time the drug has been discovered in New Zealand.
A warning has been issued by High Alert on Saturday night about an unknown white powder linked to multiple hospitalisations in Wairarapa.
Detective inspector Blair MacDonald, Manager National Drug Intelligence Bureau, said preliminary testing of the powder has indicated the presence of fentanyl, or a fentanyl-type substance.
He said police are investigating after the dozen people hospitalised are all believed to be linked to the consumption of the drug.