BEIJING (AP) -- Authorities in a Chinese city have detained the owner of a feed processing factory suspected of selling chicken feed tainted with an industrial chemical that was later found in eggs, state media reported.
The official Xinhua News Agency said late Tuesday that authorities in the northeastern city of Shenyang found that the factory mixed an ingredient tainted with melamine into feed sold to the country's leading egg producer, Dalian Hanwei Enterprise Group.
A brand of Hanwei's eggs were found earlier this month by Hong Kong food safety regulators to contain excessive levels of melamine, prompting some retailers to pull the eggs from stores in China.
Xinhua said the owner of the Mingxing Feed Processing Factory, Gao Xingtao, was detained and the remaining tainted animal feed made by the factory was destroyed.
It was unclear if the company exports its feed to other countries. Phone calls to the public security bureau in Shenyang, capital of Liaoning province, rang unanswered Wednesday, while the factory's phone number was unlisted. Chinese media reports said the factory was closed by the police.
Commonly used in plastics and fertilizers, melamine is high in nitrogen, which registers as high protein levels in quality tests. The discovery of melamine-tainted eggs in Hong Kong prompted more inspections last week that found three other brands of eggs contaminated with the chemical.
Agriculture officials have speculated that the cause was adulterated feed given to hens. No illnesses have been linked to melamine in eggs.
Other ministry officials have said that the practice of deliberately adding melamine to animal feed was widely practiced, signaling that melamine contamination may be more widespread than in just baby formula and dairy products.
Infant formula tainted with the chemical has been blamed for sickening tens of thousands of children and causing the deaths of four infants.
Though experts say at low levels it does not pose a risk to human health, higher concentrations of melamine harm the kidneys.
The Macau government said Wednesday that it had found a ninth child suffering from a kidney stone after drinking milk possibly tainted with melamine.
The government said the 5-year-old girl developed a tiny kidney stone after she took part in a school milk program supplied by Chinese dairy Yili Industrial Group Co. Yili's products were earlier confirmed to contain melamine.
Beijing had earlier pledged to overhaul the troubled industry by monitoring every link in the supply chain that brings milk from farms to family kitchens, but improving supervision of the dairy industry remained a challenge, the government said Wednesday.
Zhang Li, head of consumer goods in the Ministry of Industry and Information Technology, said in a notice on the ministry's Web site that some dairy manufacturers lacked equipment to detect the presence of melamine, partly because of cost.
Zhang said 20 percent of the country's milk producers, about 130 companies, were still shuttered amid efforts to strengthen supervision of the industry in the wake of the scandal prompted a public outcry and international recalls of many Chinese-made dairy products.
Associated Press researcher Xi Yue contributed to this report in Beijing.