Three people were taken to hospital for checks after coming into contact with an unidentified powder at the Inland Revenue's office in Christchurch this morning.
Inland Revenue Deputy Commissioner Service Delivery Naomi Ferguson said three staff members operating mail-opening machines in the Southern Processing Centre's mailroom came into contact with awhite powder substance enclosed in an envelope around 6am.
"Staff immediately implemented standard security procedures which have worked well ensuring the safety of our people," Miss Ferguson said.
They underwent decontamination as a precautionary measure, and have since been released from hospital and cleared to return to work.
The mailroom has remained cordoned off by police and has affected the processing of about 3000 returns and payments.
Other mail, that was not in the mail room at the time, is currently being processed by staff in another part of the building.
Affected customers would be contacted individually and did not need to get in touch with IRD, she said.
"This incident is obviously a concern and the department will continue to remain vigilant."
Christchurch medical officer of health Mel Brieseman said he understood the three staff members had come into contact with the powder after an envelope burst.
The powder was currently being tested and results should be available in a few days.
Christchurch Central Fire Station manager Gerry Richards said two fire trucks and two other specialist appliances were called to the scene, on Moorehouse Avenue.
A Christchurch police spokesman said a number of officers had been at the scene for more than five hours.
"We have very particular protocols for dealing with hazardous substances, and those have been followed to the letter."
