Port Stephens Council's administration office in Raymond Terrace was evacuated on Tuesday, June 2, after a white powder was found inside the building.
The white powder was detected in an envelope during the mail opening process at 8.30am. The council has a designated mail officer who opens and checks all correspondence in a specialised room to ensure the safety of staff.
Police, NSW fire and rescue and Hazmat teams were called to the scene as staff were evacuated.
The building was closed for two hours while the substance was analysed and it was found to be of no threat.
Police have indicated there have been a number of similar hoax incidents occurring across the state recently.
The council administration building has since reopened.
A letter accompanying the package contained nothing which directly threatened Port Stephens Council or the community, but both have been sent away for priority forensic analysis.
Council's General Manager, Wayne Wallis, said he was pleased with the response from staff.
"This was a credible threat and potentially a very a serious incident, but all staff responded calmly and our emergency response procedures went well," he said.
"Our response to the incident was taken seriously and executed efficiently."