Police are investigating two threatening letters containing a white powder that were sent to the American and Israeli embassies in the German capital, authorities said Tuesday.

Police spokeswoman Heidi Vogt said the two letters, sent last month, were analyzed by experts and the powder was determined to be a harmless substance.

She said police are focusing on a suspect known to them as the sender of both of the letters, but would give no further details due to the ongoing investigation. The suspect is being investigated on two counts of disturbing the peace by threatening a crime but no arrests have been made.

The Israeli Embassy received the first letter on July 24 and the U.S. Embassy the second on July 26, said police spokeswoman Kerstin Ismer.

Neither embassy had any immediate comment, saying in general they do not comment on security issues.

(AP)