A New Zealand Post building in west Auckland was evacuated after the discovery of suspicious white powder, later found to be non-hazardous.
The Fire Service said workers were moved out of the New Zealand Post delivery branch building in New Lynn after the substance was discovered on Thursday morning.
Spokesperson Jaron Phillips says the powder, a couple of teaspoons in volume, was isolated to one room of the building and ambulance staff monitored four people who may have been in contact with it.
Mr Phillips said Army explosives experts identified the powder as a non-hazardous substance, but couldn't say what it actually was.
He said the postal workers had returned to work.