Use of the drug that sparked another health scare yesterday - when it was found to have been injected into pigs - is banned in Hong Kong and in several countries overseas.
Officials in the Irish Republic discovered in 1996 that beef farmers were using the banned growth stimulant clenbuterol, and conducted a series of raids.
The drug is banned in the US and the European Union.
In 1995, clenbuterol made several people ill in Europe after they ate tainted meat.
The drug has caused no known fatalities.
If it is administered to cattle 18 days before slaughter, clenbuterol stimulates growth and changes the way digested foods are converted into fat proteins.
It causes fat stored within the muscles to be burned off as energy, producing leaner meat.
The drug is also used by athletes, particularly bodybuilders, who want to lose fat as they gain muscle.
In large doses, it can result in tension, cramps, tremors, a slightly higher-than-normal heart rate and palpitations.