Greek duo Kostas Kenteris and Katerina Thanou will discover on Monday whether they are to be expelled from the Olympics for missing a drugs test.
Officials have delayed a hearing until the pair can be released from hospital following a crash on Thursday night.
The sprinters were unavailable for testing after being allowed to leave the Olympic Village by Greek officials.
Kenteris, the 200m Olympic champion, and Thanou were then involved in a motorcycle accident.
Kenteris had been summoned to appear before Olympic officials at 1030 BST on Friday, with Thanou half-an-hour later if deemed fit enough to travel.
1615: IOC ask Greek officials to locate athletes for tests. Athletes ask for time to return to village
2030: Hellenic Olympic Committee confirm duo fail to present themselves for tests
2215: Pair crash motorbike after visiting coach
2240: IOC set up disciplinary committee to investigate case
0110: KAT hospital in Athens confirms athletes taken to hospital after crash
0530: IOC call athletes to 1030 hearing if fit enough
1030-1100: Duo fail to attend hearings; stay in hospital
All times BST
But the pair were unable to attend after being told to stay in hospital.
"Their condition is stable. They will remain in hospital for at least 48 more hours," said hospital spokesman Christos Artinopoulos.
After an emergency meeting, IOC president Jacques Rogge ordered the launch of a three-man disciplinary committee, which includes former pole vaulter Sergei Bubka, to investigate the case.
The inquiry was due to begin on Friday, with IOC medical director Patrick Schamasch visiting the sprinters to hand them a written summons.
But, after an appeal from their legal team, the IOC later announced it had delayed the disciplinary commission until Monday, two days before the athletics programme begins.
Olympic supremo Jacques Rogge confirmed Kenteris' failure to attend a drugs test in Mexico last year would not be counted as one of the two 'non-shows' required for automatic action under the IOC's own disciplinary code.
However, he admitted the issue of athletes leaving the village on their own after being notified of an impending test was one that is taken extremely seriously.
"The principle of the tests, both in and out of competition, is that you shouldn't allow the athlete (to be by) themselves because it is possible to use
"You can empty all the urine from your body and eliminate doping substances."
The news comes at the worst possible time for the host nation, just hours ahead of Friday's opening ceremony in Athens, where Kenteris was expected to light the Olympic Cauldron.
Finishes last in Euro Indoors 200m final
Wins Olympic 200m final
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Wins European 200m gold
Pulls out of Worlds with surprise late injury
Kenteris was also a candidate to be Greece's flag-bearer in Friday's opening ceremony, but that honour will now go to weightlifter Pyrros Dimas.
Rogge insisted the Games were big enough to survive the possible expulsion of the host nation's athletics hero.
"We have had big doping cases before that have not damaged the quality of the Games.
"Any athlete that we can catch, sanction and send out of the Olympic Village is a victory for sport. It strengthens the Games. The more we catch, the better it is."
Greek Olympic team spokesman, George Gakis said the motorcycle accident happened near Glyfada, a southern Athens suburb where the Greek team has its training headquarters.
Gakis said the hosts would await the outcome of the IOC's disciplinary hearing before deciding what course of action to take.
A statement from Athens' main hospital said Kenteris had suffered cranial trauma, whiplash and leg wounds, while Thanou suffered abdominal bruises, injuries to the right hip and a muscular injury to her right upper leg.
Kenteris and Thanou, who won silver in the women's 100m at Sydney, were due to attend the drug test at 1930 local time on Thursday.
Christos Tzekos, coach of the two athletes, said they were at their home at the time of the test.
Having missed it, they apparently asked to take a test later in the evening at the clinic in the Olympic Village rather than at the anti-doping laboratory in Athens.
If they fail to have a plausible excuse for failing to take the random test, they face the prospect of being expelled from the Games and serving an automatic two-year ban.
Nick Davies, media director of the International Association of Athletics, said: "What will have to be decided [by the IOC] is if it was a 'no show' - that is a surprise test which the athlete is unaware of.
"But a refusal, when an athlete does know, is a doping offence."