From Bruce Schneier’s “White Powder Anthrax Hoaxes“:
Earlier this month, there was an anthrax scare at the Indonesian embassy in Australia. Someone sent them some white powder in an envelope, which was scary enough. Then it tested positive for bacillus. The building was decontaminated, and the staff was quarantined for twelve hours. By then, tests came back negative for anthrax.
A lot of thought went into this false alarm. The attackers obviously knew that their white powder would be quickly tested for the presence of a bacterium of the bacillus family (of which anthrax is a member), but that the bacillus would have to be cultured for a couple of days before a more exact identification could be made. So even without any anthrax, they managed to cause two days of terror.
… In an interesting side note, the media have revealed for the first time that 360 “white powder” incidents have taken place since 11 September 2001. This news had been suppressed by the government, which had issued D notices to the media for all such incidents. So there has been one such incident approximately every four days — an astonishing number, given Australia’s otherwise low crime rate.