The safety of U.S. beef has once again come under question. In a recent inspection by the Department of Health, a banned substance used to promote leanness in livestock has been found in imported beef from the U.S. And some of the problematic beef products may have already entered the local market.

While examining American beef shipments several days ago, Department of Health inspectors found traces of Clenbuterol in two beef shipments totaling 228 kilograms.

As the importer immediately surrendered the shipment, none of the contaminated meat entered the market.

During subsequent inspections of American beef sold at hypermarkets in Taipei, officials found Clenbuterol in 3 of 11 samples.

According to the Food and Drug Administration, the results of secondary tests on the contaminated samples will be announced on Saturday afternoon, and the hypermarkets have already been asked to remove the beef in question from shelves.

Toxicologists say that Clenbuterol is commonly used as a decongestant and bronchodilator, and that it can cause heart palpitations, nerve damage, and even cardiac arrest when ingested by people who don't have breathing disorders.

Because the substance accumulates in animal organs and is immune to high temperatures, doctors urge anyone that develops heart palpitations after eating meat products to seek immediate medical attention.