2007 double world champion Tyson Gay, who after being tested positive for- doping test withdrawn from Moscow's World Championships, had taken a banned steroid, the BBC sports said on Friday.
The source said that they had accessed parts of a letter sent to Tyson Gay by the United States Anti Doping Agency which says that findings of a doping test sample shows values "consistent with the administration of a steroid of exogenous (external) nature."
The letter said a positive test for an "anabolic agent" of this kind would - if proven - be a violation of the World Anti-Doping Agency (Wada) code, the BBC sports reported.
USADA has been refusing to comment on whether 30-year-old Gay, who has been provisionally suspended, had tested positive for a steroid, the report said.
USADA confirmed on July 27 that Tyson Gay failed at least two tests from in and out of competition. It is understood that in addition to the positive sample he gave at the US trials in June, he failed an out-of-competition test in May, the report added.