The mailroom in the council's administration building on the corner of 3rd Ave and Cameron Rd was put into lockdown after the discovery of the package about 8.30am.
Roads were closed for several hours while hazardous materials experts removed the package and decontaminated the scene.
About 400 of the council's 660 full-time equivalent staff work from the building.
It was not the first time a suspicious powder sparked an emergency at a Bay council.
In July 27, 2015, a red powder was sent to the Western Bay of Plenty District Council's offices at Barkes Corner along with a threatening note, sparking a similar emergency response and decontamination.
Testing showed the powder was harmless.
Hazardous materials experts removed the powder from the building. Photo / File