Emergency services were called to a Royal Mail centre in Northampton after staff became concerned about a suspect package.
Staff said police, firefighters and ambulance crews were called to the building in Swan Valley last night after a package was found to have the word ‘anthrax’ on it.
However, after tests were carried out, it is understood a white powder inside was found to be harmless.
Gareth Eales, of the CWU union, said: “It was a false alarm but with good intent.
“Apparently the word anthrax was written on the front of the package so 999 was called at about 8.30pm.
“I understand the substance was actually some flour.”
Tests were carried out until the early hours of this morning but emergency services are understood to have left the site.
We received the 999 call at 9:53pm on 17 June 2013.
An East Midlands Ambulance Service (EMAS) spokeswoman said: “Several of our ambulance clinicians were dispatched to the Royal Mail premises, including our Hazardous Area Response Team. The fire and police services also attended.
“Eleven patients were assessed at the scene by our ambulance crews; two of which were decontaminated by the fire service because they’d come into direct contact with the substance which was being tested at the time to determine what it might be.
“No-one required transportation to hospital and our ambulance resources stood clear of the scene at 1:43am.”