Police in Hamburg say a white powder posted to the US consulate in Hamburg was sugar. A police spokesman said it seemed to be a bad joke.
Other packets of white powder were posted to US embassies and consulates elsewhere in Germany, as well as Denmark, Italy and Luxembourg.
The US embassy in Rome said it had received a suspicious letter containing a grainy substance.
Meanwhile US military forces in the Middle East have had their alert status upgraded as commemorations continue around the world to mark the first anniversary of the 11 September attacks in the US.
The areas affected include the Gulf, the Horn of Africa and Central Asia, including Afghanistan.
A number of US embassies in Africa and southern Asia remain closed.
