Nine anthrax scares have been reported across Australia, involving a US and British consulate as well as six other buildings and a hospital, officials said.
The US consulate in Melbourne had to be evacuated after a chemical found in a letter caused a security alarm, embassy officials said.
The British consulate in Brisbane was one of five offices in the state of Queensland to report suspicious letters containing white powder.
Six people in the Brisbane State Development Building had to be "decontaminated" by removing their clothes and showering, a Queensland Fire and Rescue Authority spokeswoman. "As yet, we don't know what the substance is," she said.
Queensland health authorities said they were investigating a possible case of anthrax in Townsville's General Hospital.
Suspicious mail was received at the State Premier's Office, at the local Griffith University, and at another building.
A post office in Sydney and a Melbourne newspaper office also had to be evacuated today after receiving suspicious letters.
Australia has offered military support to the US/British attacks on Afghanistan.
AFP