Fast food giant KFC's Chinese subsidiary pledged on Tuesday to work with authorities in investigating claims by state television that its chicken suppliers had injected anti-viral drugs and growth hormones in its poultry.

State television CCTV said that a commercial chicken producer called Liu He Zhi Tuan had been feeding antiviral drugs and growth hormones to its chickens - right up until they were slaughtered. The chickens were then supplied to KFC and McDonalds, without any kind of quality checks.