Riverina Police District is investigating after a satchel of "suspicious white powder" was opened by staff at the Riverina Mail Sorting Centre on Thursday evening.
"About 6.30pm [on Thursday], officers attached to the Riverina Police District, NSW Ambulance paramedics and NSW Fire and Rescue arrived [at a government building] to find staff had opened a satchel containing an unknown white powder," a NSW Police statement said.
"NSW Fire and Rescue HAZMAT team secured the area and confined 15 staff for decontamination, overseen by NSW Ambulance personnel.
"No staff suffered any ill effects from the exposure to the powder - which was seized and will be sent for analysis.
Turvey Park Fire Station commander Jeff Edwards said on Thursday night that firefighters "entered the building with breathing apparatuses and protected clothing to bag and tag the powder".
Mr Edward said staff had to be quarantined and decontaminated as part of a "time-consuming process and a massive interruption" that included checking and cleaning the mail centre.