Police cordoned off the building for nearly two hours before determining the grenades were inert.
A provincial police team of explosives experts was dispatched from London, Ont., but turned around when it was found the devices were non-explosive.
Coast Guard employee Lisa Kernohan says an official from Canada Post evacuated all of the federal government departments, including the Coast Guard and Transport Canada.
Police continue to investigate.
(BlackburnNews.com)Suggest a correction