Halkia is the 15th Greek athlete to test positive for methyltrienolone
Greek hurdler Fani Halkia has been formally expelled from the Beijing Olympics by the International Olympic Committee (IOC) for a doping offence.
The IOC has also urged Greek authorities to investigate her coach for possible criminal violations.
Halkia, the 2004 Olympic women's 400m hurdles champion, tested positive for the steroid methyltrienolone on 10 August before arriving in Beijing.
She flew home to Greece on Sunday but has now been officially thrown out.
Halkia is the 15th Greek athlete to have tested positive for methyltrienolone.
Under global anti-doping rules she faces a two-year ban, while the IOC has asked the Greek authorities to investigate if Greek law has been broken, particularly by her coach, George Panagiotopoulos.
Panagiotopoulos is also the coach of Greek sprinter Tassos Gousis, who tested positive for the same steroid and was sent home a few days before the Olympics.
"This decision shows the determination of the IOC to broaden the fight against doping to those behind athletes," said the IOC.
Halkia's 'B' sample came back positive for methyltrienolone, which the IOC said is a dangerous drug that "may lead to serious consequences to the health of athletes, even threatening their lives".
The IOC rejected Halkia's defence that she had never used the steroid and that her sample had been subject to "acts of tampering by third parties".
Halkia is the fourth athlete to test positive during the IOC's Beijing anti-doping program.
North Korean shooter Kim Jong Su was stripped of his silver and bronze medals after testing positive for a banned betablocker.
Spanish cyclist Isabel Moreno was expelled after testing positive for EPO in a pre-competition check and Vietnamese gymnast Thi Ngan Thuong Do was caught using a prohibited diuretic.
Halkia was a relative unknown before winning gold in Athens, where she set a new Olympic record of 52.77 seconds in the semi-finals.