If you keep poking people with sticks, eventually they will respond:

"About 10.30 this morning the brigade responded to a high-rise building at 70 Phillip Street in Sydney in relation to an unidentified substance which was come across by two workers in the basement mailroom," Supt Clough said.

"The basement was sealed off and the two workers were decontaminated before being assessed by ambulance staff and being allowed to return to work," Supt Clough said.

Meanwhile, at Parliament House in Canberra, parts of the ministerial wing adjacent to Prime Minister John Howard's courtyard were evacuated following a security scare.