Police and bomb squads have been deployed to the scene to find out the nature of the package.
"Police are at the scene and specialist teams have been deployed to determine the nature of the package," the statement issued by the police at 9.55 pm local time (6 am GMT) said.
The incident comes as the country's emergency services are in a state of high alert following a deadly mosque attack earlier this week.
The violent shooting in the mosques rocked Christchurch on Friday, leaving 49 killed and dozens injured. New Zealand's Prime Minister Jacinda Ardern called the shooting a terrorist act, saying it was the country's "darkest day."
A total of three people were detained in the wake of the attack, including the 28-year-old suspected shooter, Australian national Brenton Harrison Tarrant, who had explained his motives by his anti-Muslim and anti-migrant views in a manifesto published before the attack.
On Saturday, a court in New Zealand ruled to remand the suspected shooter in custody until April 5, while the police said they expected further charges to be brought against him.