Several embassies in the Australian capital Canberra closed on Thursday after receiving suspicious packages.
Part of the Australian parliament was also closed
The British High Commission, and the US, Japanese, Italian and South Korean embassies were shut down, but the UK mission later reopened.
Part of the parliament was also closed for the second time in a week after a package of white powder was received.
The Indonesian embassy has twice received such packages, but tests showed that the material was harmless.
"ACT (Australian Capital Territory) policing has received reports of suspicious packages at a number of foreign missions and parliament house... the packages have been secured," a police spokesman told Reuters.
The powder sent to the British High Commission and Italian embassy has been found to be harmless, police said.
Police refused to comment on the possible motive behind the incidents, but all of the diplomatic missions involved represent countries who have troops in Iraq.
"It is too early to be speculating on whether these incidents are linked or what the motive might be," a police spokesman told Reuters.
Police also refused to speculate on whether the latest packages were carried out by someone copying last week's incidents.
Last week, Australian Foreign Minister Alexander Downer received a similar package addressed to him at parliament.
Tests revealed the powder to be non-toxic.
Australian authorities have linked the packages sent to the Indonesian embassy with public anger at the jailing of a 27-year-old Australian woman for smuggling drugs into Bali.
The case of Schapelle Corby, who was given a 20-year sentence, generated huge public sympathy in Australia, with many people convinced of her innocence.