SEOUL (REUTERS) - South Korea has suspended some US beef imports after detecting the banned feed additive zilpaterol in 22 tonnes of beef supplied by a work site of Swift Beef Co, the country's food ministry said.

South Korea has suspended imports from the work site and asked the United States to verify the cause of the contamination, a food ministry statement said.

Authorities were widening tests to all beef imports from the firm, it said.

South Korea imported 75,426 tonnes of US beef from January to September, with 4,697 tonnes coming from Swift Beef.