A Ministry for Primary Industries official says he is pleased the investigation it launched following the discovery of a lone pest fly in Auckland last week has found nothing so far.
The ministry is trying to find out whether a Queensland fruit fly, found in a surveillance trap in Avondale, is part of a colony.
Deputy director general of compliance and response Andrew Coleman says an extra 150 biosecurity staff have been sent to Auckland, and 500 more traps have been installed.
He says the first two weeks are critical, and the likelihood of finding another of the insect pests is decreasing by the day.
Mr Coleman says as the ministry works through to next Wednesday it will get an indication of what the cost has been for the first two weeks of the programme.
He says New Zealand's trading partners have said they won't block fruit and vegetable exports at this stage.