NFL players are being warned about consuming meat produced in China and Mexico that potentially contains clenbuterol, which is banned under the league's performance-enhancing substance policy.
The drug-testing program's independent administrator sent a memo to players, saying "consuming large quantities of meat while visiting those particular countries may result in a positive test."
Clenbuterol is a muscle-building and weight-loss stimulant.
"Players are warned to be aware of this issue when traveling to Mexico and China," the memo read. "Please take caution if you decide to consume meat, and understand that you do so at your own risk.