Athletes at the 2011 Pan American Games face a hidden enemy in the steroid clenbuterol in Mexico's meat supply, something anti-doping officials have warned of and organizers have taken steps to address. With the games scheduled to start in Guadalajara on Friday, the World Anti-Doping Agency (WADA) issued a statement on Tuesday advising athletes traveling to Mexico to "exercise extreme caution with regards to what they eat and where they eat". WADA's advice came in the same statement in which the agency announced it had withdrawn it's appeal at the Court of Arbitration for Sport regarding a decision not to sanction five Mexican footballers who tested positive for clenbuterol earlier this year. Mexican football authorities said they believed the players ate meat contaminated with the banned drug, and WADA has now accepted that research "indicates a serious health problem in Mexico with regards to meat contaminated with clenbuterol". Clenbuterol is an anabolic steroid that is banned in sports as a performance-enhancing drug. It can also be used to fatten cattle. Such use is banned in Mexico, but WADA said that the country's government "accepts that it has an issue with contaminated meat". WADA advises athletes competing in Mexico to, if possible, "eat in cafeterias designated as safe by event organizers and also try to eat in large numbers. The state government in Guadalajara has taken steps to ensure the meat available to athletes at the Pan American Games will not be contaminated." Carlos Andrade Garin, the director of the Pan American Games Organizing Committee, offered assurances that the food available in the athletes at games venues would be free of the steroid. "It is meat that is 100 percent reliable," Andrade Garin said. "We know where it has come from and we have no doubts. The meat has been analyzed and is being watched by police to avoid any chance of contamination." Guadalajara city officials have also offered assurances regarding the city's restaurants. For Miguel Alexander Nino Rey, the doctor for Colombia's women's football team, it's not worth taking chances. "We don't plan to eat any food in town," he told AFP in the Pan American Games village, where six thousand athletes from 42 countries will be accommodated. At the same time, Nino Rey noted that the attention focused on the issue could offer an open door to actual drug cheats to claim any positive test was due to contaminated meat. Mexican judoka Karina Acosta indicated she wouldn't be quick to accept such a defence. "Tell it to someone else," she said when asked what most athletes would feel when a colleague blamed a positive test on food.