Two post shop staff members and two fire fighters were treated by fire decontamination units after an envelope with a suspicious substance was found this morning.
Tauranga fire senior station officer Mania Durham said it was unknown what the white powder in the envelope was, but fire fighters treated it as hazardous, to be safe.
It took nearly two hours to secure the site, safely isolate the powder and decontaminate the staff and fire fighters.
Traffic remained flowing on Chadwick Rd but people were kept away from the post shop during the ordeal.
EARLIER: Fire fighters are setting up the emergency decontamination unit in Greerton this morning after a suspicious envelope was spotted in the Greerton Post Shop.
Fire service northern communications shift commander Dallas Ramsay said an envelope was leaking a "powdery white substance" inside the post shop.
Three fire trucks and the Hazmat unit were in attendance, she said.