A police spokesperson said the NZ Defence Force Explosive Ordnance Disposal (EOD) unit is carrying out an assessment of the material on Atawhai Drive.
A childcare centre and marae in the area have been evacuated as a safety precaution.
"There will be a visible Police presence in the area for the next couple of hours while the NZDF's EOD unit disposes of the material safely.
"Police want to acknowledge the public for their patience and co-operation while the assessment is carried out."
The spokesperson said staff are working closely with the NZDF's EOD team to ensure the incident is managed safely.