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.
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KFC said it would punish its chicken suppliers harshly if they are found to have flouted the law by doing so.
"KFC attaches great importance to the contents of the media report and will actively cooperate with the relevant government departments' investigation," KFC said in its official online microblog.
"If (we) find out that our suppliers have conducted any illegal activity, (we) will handle it strictly," the company said.
McDonald's said in its official microblog that its chicken and raw materials pass through independent, third-party laboratory tests.
"Our chicken products comply with stringent food quality standards and comply with the relevant government standards," the company said. "Please, everyone, don't worry about eating it."
China has struggled to rein in health violations in the unruly and vast food sector despite harsh punishments and repeated vows to deal with the problem.
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The country is notorious for its food safety woes, with regular news reports of fake cooking oil, tainted milk and even watermelons that explode from absorbing too much fertilizer.
The Shanghai Food and Drug Administration is conducting tests in the poultry that has been supplied to a logistics centre in Shanghai of the KFC parent company, Yum Brands, according to state news agency Xinhua.
A Yum Brands spokesman dismissed as "untrue" media reports in late November that the supplier of 1 percent of KFC's chicken in China was giving its birds feed containing toxic additives. He declined to say whether the rumours hurt Yum's sales results.
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Yum Brands warned in November that it expected sales at established restaurants in China to fall 4 percent in the fourth quarter, despite an improvement in economic indicators such as consumer confidence and retail sales.
Yum shares are down more than 11 percent since the warning.