BEIJING (AP) -- The industrial chemical melamine is commonly added to animal feed in China to fake higher protein levels, state media reported Thursday, offering what appeared to be a tacit admission by the government that the food supply could be rife with contamination.
The Nanfang Daily said it was an "open secret" in the industry that melamine scrap is being repackaged into an inexpensive product called "protein powder" that is sold to food suppliers.
The Web sites of the official Xinhua News Agency and the Communist Party's main newspaper, the People's Daily, also carried the story in a rare step of publicizing information that reflects poorly on the country.
Safety scandals involving melamine contamination of dairy products and eggs in recent weeks have been further blows to the reputation of Chinese products, which have been under fire the past year since high levels of chemicals and additives were found in goods ranging from toothpaste to milk powder.
Four brands of Chinese eggs have been found tainted with melamine in a week, and agriculture officials speculated the source was adulterated feed given to hens.
No illnesses have been linked to eggs. But similar contamination of milk and other dairy products sent tens of thousands of Chinese children to the hospital and was linked to the deaths of four infants.
The milk scandal was blamed on dairy suppliers who added melamine to watered-down milk to dupe quality control tests and make the product appear high in protein. Melamine, a chemical used in the manufacture of plastics and fertilizer, is high in nitrogen, and most protein tests check a food product's nitrogen level.
Health experts say ingesting a small amount of melamine poses no danger, but in larger doses it can cause kidney stones and lead to kidney failure.
It is forbidden to deliberately add melamine to food and animal feed in China, but its apparent prevalence highlights the inability of authorities to keep the food production process clean of toxins despite official vows to raise safety standards.
The Ministry of Agriculture and the General Administration of Quality Supervision, Inspection and Quarantine did not respond to faxed requests for comment on Thursday's media reports. Phones rang unanswered at the Ministry of Health.
The Nanfang Daily said chemical plants used to pay companies to treat and dispose of melamine scrap, but about five years ago began selling it to manufacturers who repackaged it as "protein powder."
Initially, the inexpensive powder was used to give the impression of higher protein levels in aquatic feed, then companies started added it to feed for cattle and poultry, the report said, citing an unidentified chemical industry expert.
"The effect far more exceeds the milk powder scandal," the newspaper said.
The account was backed up by a manager reached by The Associated Press at a feed company based in central Henan province, but he added that the practice had been going on even longer than reported -- some seven or eight years.
The manager, who refused to give his name or other identifying details, citing the sensitivity of the issue, blamed suppliers to feed companies.
"It's the suppliers who do it to raise the protein level, because we put in the contract a requirement for a certain level of protein," he said. "It's very common that feed for egg-laying hens contains melamine. The suppliers add it because their ingredients for the feed are sold at a low price."
He added that his company's contract with suppliers bans them from adding melamine to their products.
Marion Nestle, a professor of nutrition, food studies and public health at New York University, said it was unlikely humans would get sick from eating meat from animals raised on melamine-tainted feed, because the amount of chemical in a few servings of meat would not be harmful.
However, she added: "It shouldn't be in the food supply at all. It's fraudulent. And the animals really can't use it for nutrition, so it's not good for the animals."
Nestle, who wrote a book about last year's pet food scandal in which a Chinese ingredient tainted with melamine sickened and killed dogs and cats in North America, said she was surprised China's government was allowing the media to admit to widespread melamine contamination.
"I view this as a sign the Chinese government is taking the food safety problem very seriously and this is the first step to doing something about it," she said by telephone.
The tainted milk scandal was a blow to China's dairy industry. Shanghai-based Bright Dairy and Food Co. reported a net loss of $39.6 million in the third quarter, compared to a profit of $57 million in the quarter a year earlier, Xinhua said Thursday.
Two other major dairy companies, Mengniu Dairy Group Co. and Yili Industrial Group Co., saw sales plummet more than 90 percent after word spread of the contamination, Xinhua said.
Associated Press researcher Xi Yue in Beijing contributed to this report.