Police and customs have seized 3kg of the potentially lethal synthetic drug compound AMB-fubinaca - with a final street value of $1.5 million.
The coroner is investigating 20 possible deaths as a result of the compound, a synthetic substance manufactured to be similar to cannabis.
Police said they found 11kg of synthetic drugs, and 1kg of AMB-fubinaca at a storage unit in Rodney.
Customs found a further 2kg of the raw compound.
Police said the 3kg could be used to make 150kg of synthetic drugs, approximately 75,000 doses, with a street value of about $1.5m.
A person has been arrested in connection with the discovery.