The World and British Anti-Doping Agencies issue a joint warning advising athletes to avoid organ meats such as liver in the upcoming 2012 Olympics as these may contain the drug clenbuterol, which is fed to livestock in some countries and is not only toxic but could disqualify them from competitions for as long as two years.

http://sports.espn.go.com/espn/wire?section=oly&id=7380018
http://sports.yahoo.com/olympics/news?slug=ycn-10738943