Anti-doping officials believe world 100 metres record holder Tim Montgomery could have taken a cocktail of drugs including human growth hormone and EPO, according to US press reports.
According to a report in the Los Angeles Times, leaked documents say that the US Anti-Doping Agency (USADA) in a letter to Montgomery allege that the American sprinter used five banned steroids plus the blood-booster EPO, human growth hormone and insulin.
USADA also suggests that Montgomery used banned performance-enhancing substances as far back as 2000, two years before he set the 100m world record of 9.78 seconds.
The newspaper said the allegations were detailed in a nine-page USADA letter sent to Montgomery on June 7th.
The existence of that letter, but not its precise contents, was made public by Montgomery's lawyers the following day.
He had until last Friday to respond to the allegations and charges could follow this week, the paper added.
The agency, according to the report, also says it "anticipates testimony" regarding use of the new steroid THG in any future case against Montgomery.
If USADA finds him guilty, Montgomery would miss the Olympics unless cleared by the Court for Arbitration in Sport (CAS).
Montgomery and his lawyers have consistently denied any wrongdoing, pointing out that he has never failed a drugs test.
His attorney, Cristina Arguedas, could not immediately be contacted for comment but has said in the past that "virtually all" the allegations are linked to the files of Victor Conte, owner of the controversial BALCO laboratory in California.
Conte was indicted after a grand federal jury hearing on charges of distributing banned substances and financial irregularities. He has offered to tell all he knows about doping among top sportsmen and women in a plea-bargain.
Arguedas pointed out that Conte and Montgomery had a "bitter" falling-out which she says makes any case from him against the sprinter unreliable.
Montgomery, the partner of triple-Olympic champion Marion Jones, was thought by U.S. commentators to have been one of at least four leading American athletes to have received a letter on June 7th from USADA regarding doping allegations.
Jones has also been investigated by USADA. No firm allegations against her have been made public.
Like Montgomery, Jones has consistently denied all doping claims against her and has never failed a drugs test.