"We just want to make sure the products on our shelves are safe. We will work closely with suppliers and the government and other related organizations to make further steps," Mu Mingming, a spokeswoman for Wal-Mart, told The Associated Press by telephone from Shenzhen.
Hanwei apologized to consumers in Hong Kong on Tuesday after testers in the Chinese territory on Saturday found its eggs contained melamine, the chemical at the heart of a tainted milk scandal that has sickened tens of thousands of Chinese children.
Hong Kong television station TVB reported Tuesday that the company's director Han Wei said the firm bore responsibility for the contamination.
"There are no consumers asking about protein levels in our eggs and so there is no need for us to add melamine to our eggs in the process of selling our products," Han said in the report. "We truly regret this. We too have an undeniable responsibility."
Calls to Hanwei, based in the northeastern port city Dalian, went unanswered Tuesday, but an official with the city government said Hanwei had started a nationwide recall of eggs deemed "problematic." The official, who refused to give her name as is common among Chinese officials, said she had no further details.
Han did not explain how the chemical made its way into eggs sold by the company. But the Chinese Agriculture Ministry's animal husbandry department head, Wang Zhicai, was quoted by the Beijing News newspaper Tuesday as saying it was highly likely that melamine had been added to the feed given to the chickens that laid the eggs.
Melamine, a chemical used in plastics and fertilizer, is not an animal feed additive and is banned from being mixed in, Wang said.
The report said the ministry has been inspecting feed for the chemical since last year, after a Chinese-made pet food ingredient containing melamine that was linked to the deaths of dozens of dogs and cats in the United States and touched off a massive pet food recall.
Last week, the death of 1,500 raccoon dogs in China was blamed on feed tainted with melamine.
It was not immediately clear why the chemical would be added into animal feed. But a food industry expert pointed to the same motivation cited in the current milk scandal and last year's pet food recall: Melamine boosts nitrogen levels, making products seem higher in protein when tested.
Jason Yan, the U.S. Grains Council's technical director in Beijing, said the chemical could have been added by suppliers of animal feed ingredients trying to pass off a normal grade protein ingredient as a higher grade product.
"The price gap between the two grades is high," about several hundred yuan (tens of dollars) per ton (metric ton), Yan said Tuesday. "Some traders may be willing to take the risk by adding melamine to make a lot more profit."
Wang was quoted as saying that there was little available research on the human effects of eating eggs tainted with melamine. Milk formula contaminated with the chemical has given Chinese babies painful kidney stones.
More than 3,600 children remain sick from tainted milk, with three in serious condition, the Ministry of Health said last week. The deaths of four babies were also linked to compromised dairy products.
Hong Kong testers found melamine in the eggs at nearly two times the territory's legal limit for the chemical in foodstuffs. The egg contamination has prompted Hong Kong officials to expand food testing to Chinese meat imports.------
Associated Press researcher Xi Yue contributed to this report in Beijing.