Back-up tests on samples by 11 out 14 members of Greece's weightlifting team have also detected banned drugs.
The initial positive test results were revealed on 4 April, prompting the suspension and resignation of national coach Christos Iacovou.
Greece could now find itself without a weightlifting team at the Olympic Games in Beijing in August.
Since the 1992 Barcelona Games, Greeks have won 12 Olympic weightlifting medals, including five golds.
Prior to Barcelona, the country had not won a weightlifting medal since the 1904 Games.
Iacovou, a former weightlifter himself, had been in charge of the national team since the 1992 Olympics.
The Greek federation said out-of-competition drugs tests were conducted by the World Anti-Doping Agency on the orders of the International Weightlifting Federation.