Hong Kong officials announced that for the second time in a week they have found a batch of eggs imported from China that contain high levels of melamine.

The announcement, which came late Tuesday from the territory's food safety agency, is adding to concerns that melamine contamination may be more widespread in China's food supplies.

While Hong Kong officials cautioned that children and adults would have to eat a large number of tainted eggs in a single day to fall ill, the report is another blow to China's agriculture industry.

Chinese regulators say they are now investigating how melamine got into eggs. The government is also doing spot checks in supermarkets in some cities, like  Shanghai.

Zhang Zhongjun, an official in Beijing with the United Nations Food and Agriculture Organization, said he met Wednesday with officials from China's Agriculture Ministry and was told they believed the problem eggs in Hong Kong were probably contaminated by melamine-tainted animal feed.

But Zhang said the government told him the source of the contamination was not yet known. "It's not clear whether the melamine was added by humans or by pollution," he said.

Food safety officials said that if chicken feed is contaminated, it is possible hog and fish feed could be also.

On Monday, Wal-Mart Stores said some of its stores had pulled the Hanwei brand of eggs from shelves in China as a precaution after the Hong Kong government’s finding.

The first batch of eggs that tested positive for high melamine levels by the Hong Kong Center for Food Safety came from a company in Dalian, in northeast China. Officials from the region told Xinhua, the government news agency, that the contamination may have come from local poultry farms.

According to a notice posted on the web site of the Dalian Hanwei Food Co., regulators learned on Sept. 27 that some eggs were contaminated. The company said it was ordered to recall eggs, and exports to Hong Kong were halted by regulators in early October.

The second batch of tainted eggs found in Hong Kong was from the Jingshan Agriproducts Company in Hubei Province. Pan Fengxia, the company's general manager, confirmed by telephone Wednesday that eggs tested in Hong Kong were found to have higher levels of melamine than permitted, but she did not know why. "I never heard that melamine was added into feed or my products," she said.