As of October 30, eggs produced by four Chinese companies have been found to be contaminated by melamine, the industrial chemical at the center of China's recent tainted milk scandal.

Poultry feed is being blamed as the source of contamination.

The Hong Kong secretary for food and health York Chow confirmed October 30 that the Hong Kong Center for Food Safety (CFS) found excessive levels of melamine in three brands of eggs from the mainland.

On October 25, CFS said it has found high levels of melamine in eggs produced by the Dalian Hanwei Enterprise Group based in Liaoning Province. The eggs contained 4.7 parts per million (PPM) of melamine, almost double the 2.5 PPM legal limit for melamine in Hong Kong.

A few days later, the center again found tainted eggs from the Jingshan Pengchang Agriculture Product Company and Jingzhou Shuanggang Poultry Company, both of which are based in Hubei province. The Hong Kong authority has put a halt on sale of those eggs.

York Chow said the Hong Kong authority has informed the General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) of its findings, calling on Beijing to tighten supervision of domestic egg producers.

Eggs produced by Dalian Hanwei have been recalled in the mainland market. All eggs from Jingshan Pengchang and Jingzhou Shuanggang were exported.

Caijing learned that early on September 27, several batches of eggs produced by Dalian Hanwei were found to be contaminated by Liaoning food safety inspectors. However, the department didn't publish in a timely manner.

Caijing also found that in early October, the Liaoning animal supervision department launched investigations into Shengyang Xinmin Mingxing Feed Company, the poultry feed supplier of Dalian Hanwei. The department found melamine in feed produced by Xinmin Mingxing, which led to the detainment of the company’s manager.

However, no nationwide inspection on egg was launched at that time. It wasn’t until late October when tainted eggs were reported in Hong Kong, that several cities including Beijing and Hangzhou started testing egg samples.

Since then, melamine was found in Xiang Yun brand eggs in Hangzhou. No other tainted eggs have been reported in the mainland market.

Following in close succession the tainted milk scandal, the unfolding egg case again reveals holes in China's food safety supervision system, in which responsibility is spread dangerously thin among many different government agencies.

A spokesperson of the Ministry of Health told Caijing on October 30 that the egg case should be supervised by the Ministry of Agriculture, rather than the Ministry of Health.

An official from the AQSIQ also alleged that it is agricultural department’s responsibility to monitor egg quality.

Caijing tried to contact the Ministry of Agriculture about the progress of investigation, but they have not been available for comment.