The Food and Drug Administration (FDA) confirmed the presence of 'trace amounts' of melamine in a US-manufactured infant formula. The toxic chemical has sickened tens of thousands of infants in China, and killed four - the faked formula having large amounts of melamine added to watered-down milk, to make it appear to have appropriate protein content.

The trace amounts of melamine and its by-product, cyanuric acid, were found in formula from Abbott Laboratories, Nestle and Mead Johnson, which together make more than 90% of all infant formula produced in the United States.

However, FDA said the levels of melamine found in the 77 samples tested were 10,000 times lower than those found in Chinese-made formula. The contamination is believed to be the result of the manufacturing process, as melamine is approved for use in can liners.

The FDA believes the melamine contamination in the US-made formula was not intentional. Since melamine is used in some plastic food packaging and some equipment cleaning solutions, it could possibly leach into food products. Moreover, the agency said last month that it could not set an acceptable level for melamine in infant formula because the way it affects infants' kidneys is not fully understood.

Stephanie Kwisnek, with the FDA's Center for Food Safety & Applied Nutrition stressed that the agency believes US-produced infant formula is "safe", and there are no plans for recalls. She said: "There's no concern for public health. FDA's advice to parents is to continue to use the infant formula. It is safe, effective, and wholesome. There's no health risk."