The war against drugs in sport thrust five other athletes into the spotlight yesterday as Athens put the final touches to preparations for the 2004 Olympics.

The attention turned to US sprinter Bernard Williams, two Greek baseball players, a Swiss cyclist, and a Spanish canoeist.

Williams, a gold medallist at the Sydney Games in the 4x100 metres relay, tested positive for a metabolite of cannabis, prohibited substance under the International Association of Athletics Federations (IAAF) rules, at a meeting in Spain in June.

He has received a public warning for a first offence, but remains eligible to run in Athens, the United States Anti-Doping Agency said.

Earlier, Swiss cyclist Oscar Camenzind was also named and shamed after testing positive for the same blood-boosting substance which enhances endurance. His Swiss professional team, Phonak, reacted by firing the rider.

The Swiss Olympic Association said in a statement the 1998 world road race champion had agreed to withdraw from the Games after being notified of the result of a urine test conducted in training last month.

Under Swiss rules, anyone who tests positive is banned with immediate effect even before the result of a second sample.

The list of offenders grew with Spanish canoeist Jovino Gonzalez also testing positive for EPO. A Spanish Sports Council spokesman said he had been dropped from the Olympic team and would not be replaced.

Greece's Olympic authorities said Greek-American baseballers Derek Nicholson and Andrew James Brack had tested positive for banned substances.

Only slightly easing their discomfort was the fact that, as members of the Greek baseball team, both had been imported from North America and handed citizenship especially for the Games. The team is bankrolled by Peter Angelos, the multi-millionaire Greek-American owner of the Baltimore Orioles.

"It's very sad to be standing before you today talking about doping," Greek Olympic team chief Yiannis Papadoyiannakis told reporters.

Athletes who fail a drugs test can expect to be banned for at least two years. The Athens Olympics are the first Games since the introduction of a global anti-doping code.

As the two Greek baseball players awaited a second test, Papadoyiannakis disclosed the world anti-doping body WADA had demanded detailed information on a host of Greece's top Olympic competitors.

"We will fully co-operate with WADA," he said. "The Greek team will crack down on doping wherever we find it."

The International Olympic Committee (IOC) said last week dope testers had extended blood sampling to all Olympic sports for the first time after being previously limited to endurance sports.

IOC officials say more than 3,000 tests will be conducted in Athens, a 25 per cent increase from the 2000 Sydney Games.

The US athletics team has been battered more than most by doping controversy in the past few months, with four track and field athletes suspended for two years after an investigation into the Balco laboratory in California.

The US team for Athens still includes world 100 metres champion Torri Edwards, who awaits a decision on a positive test for the banned stimulant nikethamide.

Edwards plans to appeal to the Court of Arbitration for Sport against her two-year doping ban in a final attempt to be allowed to run in Athens.

The Guardian revealed last week that the American had been found guilty by the IAAF after testing positive for a banned stimulant at a meeting in Martinique in April.

Triple Olympic champion Marion Jones is still under investigation by USADA.