Ms Urwin said three of the passengers confessed they were Chinese nationals.
They claimed to have paid the fourth passenger to be smuggled into South America via New Zealand, she said.
"The result of this operation is a testament to the fantastic job carried out by our immigration staff in close consultation with Customs officers at the border every day.
"While New Zealand was not the target of the smuggling this time it could be a different story next time.''
The three Chinese nationals were returned to China last night after a search by Customs found their genuine passports in their baggage.
The alleged people smuggler was a Malaysian citizen who was travelling on a genuine passport, Immigration New Zealand said.
He can not be prosecuted under New Zealand law as he and the other passengers were not attempting to enter the country.
The man was being held at the airport ahead of a transfer back to Malaysia.