The 11 suspicious envelopes found at a Piraeus courthouse complex on Thursday that prompted a mobilization of the police and fire brigade were to be examined Friday by state laboratories.
A preliminary examination by bomb disposal experts on Thursday showed that the envelopes did not contain explosives.
One of the envelopes reportedly contained a powdery substance.
According to reports Friday the envelopes were sent from different parts of Greece.
Last month, dozens of universities around the country received envelopes in the mail containing a chemical substance used in the production of industrial adhesives.