The Mexican government says it has suspended butchering of cows at a slaughterhouse in central Mexico after finding many of the cattle there tested positive for clenbuterol.
The federal Health Department says 68 percent of the livestock at the slaughterhouse in Cuernavaca had the anabolic agent.
Clenbuterol is banned for use on animals in Mexico, where President Felipe Calderon has acknowledged it is used to bulk up livestock.
A Health Department statement Thursday says authorities seized 10 tons of contaminated meat at the slaughterhouse.
Last month, five Mexico soccer players tested positive for clenbuterol in pre-competition testing at the Gold Cup. Soccer officials blamed the results on contaminated meat.