American sprinter Bernard Williams tested positive for a metabolite of cannabis at a meeting in Seville in June, the U.S. Anti-Doping Agency (USADA) said on Monday.
Williams, a gold medal winner in the U.S. 4x100 relay team at the Sydney Olympics, has received a warning but remains eligible to compete in Athens.
A USADA statement said Williams had tested positive for a metabolite of cannabis or tetrahydrocannabinol (THC), a prohibited substance under the International Association of Athletics Federations (IAAF) rules.
It added: "Following consultation with the IAAF, Williams, 26, received a public warning, in accordance with the IAAF rules for a first offence.
"In addition, he is disqualified from his second-place finish in the 200 metres at the (Seville) meeting. Williams is eligible to compete at the 2004 Olympic Games in Athens."
The statement said that in accordance with the USADA Protocol for Olympic Movement Testing, the case was referred to USADA on August 3 for adjudication from the USA Track and Field (USATF), which received the case from the IAAF.
USADA became the independent anti-doping agency for U.S. athletes for the Olympic movement in October 2000.