Several people were evacuated from Parliament after a white substance was found in an envelope on Wednesday.
The envelope was sent to the eighth floor of the Beehive, which houses the staff of the prime minister and the Department of Prime Minister and Cabinet.
Part of the eighth floor was been cordoned off, several people were evacuated, and a cordon was set up around Parliament's forecourt.
Prime Minister Helen Clark was not in Wellington on Wednesday.
Four fire engines, several police vehicles and an ambulance were in Parliament's forecourt at midday, but the building was operating as normal.
Two firefighters in full breathing apparatus left the building carrying a container.
The cordon around the forecourt was lifted about 1pm, though part of the eighth floor will remain cordoned off until the powder can be identified.