American cyclist Tyler Hamilton has surrendered his 2004 Olympic gold medal after confessing to doping, the U.S. Anti-Doping Agency (USADA) said on Friday.
"I can confirm that Tyler Hamilton has given his gold medal from the 2004 Athens Olympic Games to USADA and that we will continue to work with the IOC and the USOC as appropriate concerning the final implications of our overall investigation," USADA chief executive Travis Tygart said in a statement.
The International Olympic Committee (IOC) earlier on Friday said it also was studying the issue.
"The IOC has taken note of Hamilton's confession and will of course study any potential Games-related implications," it said.
Hamilton won cycling's time-trial at the Athens Olympics and was allowed to keep his medal after testing positive for blood doping because the laboratory accidently destroyed his B sample by deep freezing it.
In an interview to be aired by the television program "60 Minutes" on Sunday, Hamilton ended years of denials by admitting to using performance-enhancing drugs, but said he was not alone.
The 40-year-old said he witnessed former team mate Lance Armstrong inject himself with a blood-booster during the 1999 Tour de France, which Armstrong won.
Armstrong, who won the Tour de France seven times, has always denied taking banned substances but has repeatedly had to fend off accusations despite having never failed a drugs test.
His lawyer Mark Fabiani told Reuters on Thursday that Hamilton's accusations about Armstrong were untrue.
Tygart said USADA was continuing its ongoing investigation in cycling.
"Where there is credible evidence of doping, a fair and thorough process exists for resolving such violations," he said.
"We do not comment on the substance of an active investigation, but as always we remain committed to protecting the rights of clean athletes and preserving the integrity of sport."
The U.S. Olympic Committee referred all queries to USADA.