Antonio Pettigrew, who was stripped of the 2000 Olympic 4x400m relay gold medal for doping, died at the age of 42 in his car.
Authorities said on Tuesday that his death could have been accident or suicide as he was found dead in the back seat of his car in Chapel Hill, North Carolina.
Chatham County Sheriff's major Gary Blankenship said that his car was locked and there was evidence that Pettigrew had taken sleeping pills without sign of foul play.
Two friends discovered his car en his route between his home and the University of North Carolina where he was an assistant athletics coach.
Pettigrew, who won the 1991 400m world title in Tokyo, was a member of the 4x400 metres US relay team that won the gold medal at the 2000 Sydney Olympics.
But the International Olympic Committee (IOC) stripped Pettigrew and his teammates - including legend Michael Johnson - of their medals after he admitted to doping during a trial against former coach Trevor Graham.