U.S. sprinter Jerome Young acknowledged Thursday that he tested positive in 1999 for a banned steroid but competed at the 2000 Sydney Olympics after being cleared by U.S. track authorities even as the International Olympic Committee "strongly" urged U.S. Olympic and international track officials to investigate, the Los Angeles Times reported in its Friday editions.

Young, 27, of Fort Worth, who won the 400 meters Tuesday in the world championships at Paris and was part of the gold-medal winning U.S. 1,600-meter relay team at Sydney, said in an interview with the Times, referring to the failed 1999 drug test, "It's something that happened. It's all past, and it's something I don't want to talk about. Not at all."

IOC president Jacques Rogge sent a letter Thursday to the U.S. Olympic Committee and the International Association of Athletics Federations "strongly urging them to pursue the matter."

Dick Pound, president of the anti-doping agency, said Wednesday that the legitimacy of the U.S. victory was "shattered" by the report and called for the team's medals to be stripped.

John Coates, the president of the Australian Olympic Committee and a senior official in the organizing of the Sydney Games, told Australian Associated Press, "I fully support Dick Pound's stance and await the outcome of any investigation that might be held."

Despite the heat, Young told the newspaper, "I'm still keeping my head up.

"Yes, it's something that happened," he continued, meaning the 1999 positive test for the steroid nandrolone. "But it's something that I've ... I've moved on. It's something I don't want to talk about. ... It's something that's a closed door. I don't even think about it now. ... I'm keeping focused. I don't let things distract me."

Young's comments, in conjunction with the call to action by the IOC, mark a significant upturn in the intensity of the matter, the Times said -- setting the stage for what could be a close and emotionally charged review of the case, and of U.S. policies, by American, international and Olympic authorities.

The newspaper said the medals -- and likely the U.S.'s reputation, as well -- are at stake.

Michael Johnson, who anchored the winning 1,600-meter relay team in Sydney, told the French newspaper L'Equipe in a story published Thursday that authorities " ... will never have my medal." The newspaper said he made the comment in a joking manner.

It had been known that an American athlete tested positive before the Sydney Olympics, was exonerated by U.S. officials and won a gold medal. U.S. Olympic and track and field officials refused to disclose the name.

"All along in this affair, the IOC has constantly pushed for the unnamed athlete's identity to be disclosed, together with all the details of the case," the IOC said.

If the allegations against Young are true, "they would lift the suspicion that hangs over innocent athletes," the IOC added.

Information from The Associated Press was used in this report.