BEIJING — Reigning women's 400-meter hurdles champion Fani Halkia of Greece will not defend her Olympic title in Beijing after becoming the latest Greek athlete to fail a doping test.

The International Olympic Committee confirmed Sunday that Halkia tested positive for a steroid at a Greek athletics team training camp in Japan before coming to Beijing.

Halkia is the fourth athlete to test positive during the IOC's Beijing anti-doping program.

Greek Olympic officials said she had withdrawn from the games and was flying home Sunday.

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.

Falkia's test was conducted by the World Anti-Doping Agency on Aug. 10 under the auspices of the IOC, which set up a disciplinary commission to deal with the case.

"We can test athletes anywhere and at any time, wherever they are in the world," an IOC spokeswoman, Emmanuelle Moreau, said. "We will follow the normal procedures. The disciplinary commission will meet in the coming days."

Halkia told reporters early Sunday in Beijing she was "shocked" to learn she had tested positive for the banned substance methyltrienolone and would be unable to defend her gold medal.

"I have undergone more testing than anyone else," she told Greek reporters.

Halkia said she had volunteered to take part in WADA's pilot program in which athletes submit themselves voluntarily to regular testing.

The Greek Olympic committee said the athlete had been suspended pending the results of the backup "B" sample.

Halkia left China a few hours before the first round of the women's 400 hurdles. She was a relative unknown before winning gold in Athens, where her semifinal time of 52.77 established an Olympic record.

Halkia is the 15th Greek athlete to have tested positive for methyltrienolone. The list includes 11 weightlifters, swimmer Yannis Drymonakos, 400-meter runner Dimitrios Regas, and sprinter Tassos Gousis, who was sent home a few days before the Olympics.

The IOC also barred Greek sprinter Katerina Thanou from Beijing for evading drug tests before the 2004 Athens Games.

The IOC is conducting a record 4,500 drug tests in Beijing, up from 3,600 in Athens.

The testing program began with the opening of the Olympic village on July 27 and runs through the end of the games on Aug. 24.