Greece's two top track and field stars have pulled out of the Athens Olympics after apologizing to their embarrassed nation for a scandal that arose after they missed drug tests.

Kostas Kenteris, the reigning Olympic 200-meter champion and his training partner, Katerina Thanou, who won silver in the women's 100-meters at the last Olympics in Sydney, were Greece's biggest hopefuls for track and field gold in Athens.

But both of them walked out on the Athens Games moments after appearing before an International Olympic Committee disciplinary hearing. The committee was expected to have banned them from competing, but spokeswoman Giselle Davies says it will take no action against the two sprinters because they had abandoned the tournament.

"The athletes' unequivocal surrender this morning of their accreditation means that the IOC's sanction of expulsion from the Games becomes a moot point," she said.

Kenteris and Thanou have been under suspicion since last Thursday when they missed a drug test at the Olympic village. Hours later, they checked into a hospital where they told doctors they had been involved in a motorbike accident. But there were no witnesses to the crash, and it is still unclear how they got to the hospital.

The Greek news media have been demanding clear answers, and the two former idols, now fallen heroes, are being blamed for casting a cloud over the opening ceremonies last Friday and tarnishing Greek honor.

Kenteris told reporters why he had decided to pull out of the Games. He said that a sense of responsibility and respect for the national interest motivated his decision.

But he said he was never notified that he had to show up at the drug test last Thursday. And he insisted that he has never used banned substances.

Thanou said she, too, would not compete. And she apologized to her fellow Greeks for not being able to take part in the Games, which have returned to the country of their birth for the first time in more than a century.