Australian police said on Thursday they had arrested a 48-year-old man for sending as many as 38 suspicious packages to diplomatic embassies and consulates across the country.
The man was charged with sending dangerous articles through a postal service and the maximum penalty for the offense is 10 years imprisonment, the Australian Federal Police said in a statement.
There was no ongoing threat to the general public, the AFP said.
Police have so far recovered 29 of the 38 parcels but are yet to determine the exact composition of the material in them.
Australian media reported on Wednesday the parcels appeared to contain plastic bags of concrete and asbestos, with "asbestos" written on at least one of the bags.
The Age newspaper reported that one firefighter was seen outside the South Korean consulate carrying a large plastic bag with the word "asbestos" written on it.
Other missions in Melbourne reported by media to have received suspicious packages included those representing Greece, Italy, Spain, Thailand, India, Japan, Pakistan, Egypt, Denmark and Switzerland. Reuters could not confirm the reports.
Australia's Department of Foreign Affairs and Trade (DFAT) said it had sent an email to all diplomatic missions in Canberra earlier this week after three offices in the capital and Sydney received suspicious packages.
It subsequently sent similar advice to missions around Australia.
"The note advised missions to handle mail in accordance with their own government's protocols and instructions," a DFAT spokesman said.