Chinese protein export contamination was first identified after the wide recall of many brands of cat and dog food starting in March 2007 (the 2007 pet food recalls), and eventually involved the human food supply, though no evidence of harm to human health has been adduced to this point. The recalls in North America, Europe and South Africa came in response to reports of renal failure in pets. Initially the recalls were associated with the consumption of mostly wet pet foods made with wheat gluten from a single Chinese company. In the following weeks, several other companies who received the contaminated wheat gluten also voluntarily recalled dozens of pet food brands. One month after the initial recall, contaminated rice protein from a different source in China was also identified as being associated with kidney failure in pets in the United States, while contaminated corn gluten was associated with kidney failure with pets in South Africa.The Chinese government was initially slow to respond. Both government officials and manufacturers went so far as to deny that vegetable protein was even exported from China and refused for weeks to allow foreign food safety investigators to enter the country. Ultimately, the Chinese government acknowledged that contamination had occurred and arrested the managers of two protein manufacturers identified so far and took other measures to improve food safety and product quality.The first and most easily identifed contaminant in the vegetable protein is melamine. However, melamine is not considered to be especially dangerous to animals or humans, and so investigators have continued to examine the role of other contaminants found to be present in the proteins, including cyanuric acid. Current research has focused on the combination of melamine and cyanuric acid in causing renal failure. Reports that cyanuric acid may be an independently and potentially widely-used adulterant in China have heightened concerns for both pet and human health.Both the wheat gluten and rice protein concentrate were found to actually be wheat flour, which contains wheat gluten as a component and is less expensive than separated gluten. Melamine and cyanuric acid were most likely added to fraudulently increase the apparent protein content of the flour to allow them to pass as concentrated vegetable proteins.Reports of widespead adulteration of Chinese animal feed with melamine have raised the issue of melamine contamination in the human food supply both in China and abroad. On April 27 US FDA subjected all vegetable proteins imported from China, intended for human or animal consumption, to detention without physical examination, including: Wheat Gluten, Rice Gluten, Rice Protein, Rice Protein Concentrate, Corn Gluten, Corn Gluten Meal, Corn By-Products, Soy Protein, Soy Gluten, Proteins (includes amino acids and protein hydrosylates), and Mung Bean Protein. In a teleconference with reporters on May 1, officials from the FDA and U.S. Department of Agriculture said that between 2.5 and 3 million people in the United States had consumed chickens that had consumed feed containing contaminated vegetable protein from China. Reports that melamine has been added as a binder in animal feed manufactured in North America also raise the possibility that harmful melamine contamination might not be limited to China.There has been widespread public outrage and calls for government regulation of pet foods, which had previously been self-regulated by pet food manufacturers. The United States Senate held an oversight hearing on the matter by April 12. The economic impact on the pet food market has been extensive, with Menu Foods losing roughly $30 million alone from the recall.As of May 7, United States food safety officials stated: "There is very low risk to human health from consuming meat from hogs and chickens known to have been fed animal feed supplemented with pet food scraps that contained melamine and melamine-related compounds"