SEOUL, South Korea – Trade officials in South Korea suspended some imports of US beef supplied by Greeley, Colo.-based JBS USA, after zilpaterol was found in the meat, according to a Reuters report. Many Asian countries have banned feed additives such as zilpaterol.

South Korea's food ministry halted imports from Swift, and asked the United States to launch an investigation. South Korea imported 75,426 tonnes of US beef from January to September; of that amount 4,697 tonnes came from Swift Beef, according to Reuters.

Zilmax [zilpaterol hydrochloride] came under intense scrutiny after Springdale, Ark.-based Tyson Foods, Inc. announced it would stop buying cattle fed zilpaterol on concerns the feed additive was causing lameness and negatively impacting the quality of beef. Merck Animal Health, which manufactured Zilmax, stopped sales of the product in August and announced it would conduct a scientific audit to monitor the process of feeding Zilmax to cattle.