The authorities may revise production standards for animal feed after excessive levels of melamine were found in eggs exported to Hong Kong, sources with the Ministry of Agriculture said.

The industrial chemical has been at the heart of the tainted-milk scandal that has made tens of thousands of Chinese children ill - but current rules set no limit for melamine content in animal feed.

Although testing for melamine is recommended, it is not compulsory, leaving loopholes in the production process, an official with the ministry was quoted by Xinmin.cn website as saying yesterday.