Four fire crews and a decontamination team are at Auckland Airport, where an unidentified substance has been found.
The Fire Service said the substance was found in a suspicious package at a warehouse at the airport.
It said ambulance staff were assessing one person who came into contact with the substance.
The Fire Service said the package had been taken from the building in an air-tight drum by the Defence Force.
It is still unclear what the substance is but the Fire Service said it had tested negative for anthrax.
St John Ambulance said it had treated two people for minor complaints and they will not be taken to hospital.
The police are expected to release more information soon.