Wal-Mart has pulled a major brand of eggs from its stores in China as a precaution after an announcement from Hong Kong authorities that the eggs had been found to contain melamine, the same chemical at the heart of the contaminated milk scandal.

The revelation that melamine has also been found in eggs has led to questions on whether the chemical, which is normally used to make plastics, had been mixed into livestock feed and contaminated China's wider food chain.

According to Zhang Zhongjun, program officer with the United Nations Food and Agricultural Organization, if the feed is found to be contaminated, then there is the possibility that pork, chicken, fish, and beef could also be contaminated.

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