HONG KONG, Sept 9 | Thu Sep 8, 2011 7:51pm EDT

HONG KONG, Sept 9 (Reuters) - China Yurun Food Group Ltd said on Friday one live hog at a subsidiary in China had tested positive for clenbuterol, an illegal additive in pig feed fed to animals to keep their meat lean.

In a filing to the Hong Kong bourse, the Chinese meat processor said subsidiary Henan Yurun Beixu Food Co Ltd had on Sept 1 discovered one live hog that tested positive for clenbuterol among a batch of live hogs from a supplier.

The hog was destroyed, and test results showed all other raw pork products produced on the same day met relevant national standards and did not contain any traces of clenbuterol, the company said.

Shares of China Yurun Food dropped 16.1 percent on Thursday to the lowest in two years, hit once again by worries over quality issues. An unconfirmed report in the National Business Daily said meat from the company's Henan unit contained additives.

In July, Yurun had suspended production at a plant in a Chinese province due to problems with the meat it produced.

(Reporting by Donny Kwok; Editing by Jonathan Hopfner)