Two Greerton women and two fire fighters had to be decontaminated by a hazardous substances unit after coming into contact with an unidentified white powder.
The two Greerton PostShop staff got a nasty surprise when they discovered the unknown substance leaking from an envelope while sorting the mail about 8am yesterday.
The scare prompted a full emergency service response and took about an hour and a half for fire fighters to contain and isolate.
Three fire trucks and a hazmat truck were at the scene.