Contaminated beef can be a legitimate excuse for clenbuterol in an athlete’s blood sample, the World Anti-Doping Agency said Wednesday, in a decision regarding five soccer players who blamed their positive test results on eating Mexican beef. Whether a similar excuse will stand up for the Spanish beef that Alberto Contador claims caused his positive test at the 2010 Tour de France remains to be seen.

WADA reversed course Wednesday when it withdrew its appeal of a FIFA decision to absolve five Mexican soccer players of doping charges. WADA said recent evidence lends credibility to the players’ explanation.

“WADA has subsequently received compelling evidence … that indicates a serious health problem in Mexico with regards to meat contaminated with clenbuterol. This is a public health issue that is now being addressed urgently by the Mexican government,” WADA said in a statement.

The players were suspended at a Gold Cup tournament in June and claimed that the positive samples were the result of meat they ate at a training camp ahead of the tournament.

The Mexican Football Federation decided not to sanction the players and WADA appealed that decision to the Court of Arbitration for Sport. But WADA reversed course after reviewing evidence presented by FIFA.

Ongoing problem in Mexico — what about the Pan Am Games?

“The government of Mexico – which has legislation forbidding the use of steroids with livestock – accepts that it has an issue with contaminated meat and is actively looking to resolve the problem state by state. Already several arrests have been made pursuant to these laws and large amounts of clenbuterol seized. Investigations are to continue,” WADA said.

The Pan American Games open in Guadalajara on Thursday, and WADA cautions athletes to “exercise extreme caution with regards to what they eat and where they eat.

“If possible, they should 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.”

Contador’s case goes before CAS next month. WADA made clear in its statement that its decision regarding the soccer players will not necessarily apply to the cyclist.

“Clenbuterol remains a prohibited substance and WADA will approach and study any positive case on an individual basis,” the agency concluded its statement.