The US Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS) announced the recall from a plant in Illinois, USA was due to the finding of Ivermectin, an antiparasitic medicine used to rid live animals of worms.

This recall follows one made in May when residues of Ivermectin were also found to be above US Food and Drug Administration limits. Testing has revealed Brazilian beef processing plants to be the source of the drug.
This has led to a de-listing of 24 such plants, and the Brazilian government is currently halting its export of processed beef to the US.

The USDA has reported that Ivermectin residues in meat poses a risk of neurotoxicity in humans, leading to potential nerve damage and inability to coordinate movements.

We are thankful, US agencies for this alarming yet crucial announcement of a meat recall. Our prayers that such information leads more and more people to realize the health and safety of humane plant-based fare.

http://www.foodsafetynews.com/2010/06/brazilian-beef-products-recalled-for-drug-residues/
http://www.foodsafetynews.com/2010/06/consumer-group-investigate-drug-residues-in-meat-from-brazil/