The fourth floor of the building at 1 The Terrace in Wellington, occupied by the director general of the Ministry of Health, was ordered closed at 12:20 p.m. The incident affected about 80 people, The (Wellington) Dominion Post reported.
The alert was sparked by a letter containing unidentified white powder, which arrived Friday but was opened Monday, police Senior Sgt. Hamish Milne said.
"Three people were exposed to an unidentified, but what now has been determined as, an inert white powder," Milne said, adding the powder was examined by the New Zealand military.
It was the sixth time a suspicious package containing white powder has been sent in the past several days, with packages arriving at the officers of Parliament members, a hospital and the French Embassy, the newspaper said.