US health officials have found trace amounts of the chemical melamine in one sample of infant formula sold in the United States, a Food and Drug Administration spokeswoman said on Tuesday.

"There's no basis for concern because we're talking about trace levels that are so low ... that there's absolutely no risk," FDA spokeswoman Judy Leon said.

The chemical is normally used to make plastics. Melamine's ability to make foods appear to have higher amounts of protein during testing has made it a cheap but dangerous substitute that can damage the kidneys.

But Leon said that was not the case with the US infant formula. The new results "are most likely a result of the manufacturing process or what comes into contact with formula in cans. It's not adulteration and it's not contamination," she said.

Leon declined to name the manufacturer of the sample found to contain melamine. US-approved makers include Abbott Nutrition, Bristol-Myers Squibb unit Mead Johnson Nutritionals and Nestle USA.

Industry trade group the International Formula Council sought to reassure consumers.

"Infant formula manufactured in the United States remains safe and nutritious," the group said in a statement. "US infant formula products meet the highest standards and specifications."

Mead Johnson Nutritionals, the maker of Enfamil baby formula, said that by testing samples of its products and raw materials using published FDA methodology, it had not detected any level of melamine.

Leon said the FDA has deployed more sensitive tests in recent weeks as it has expanded tests for melamine in all food products, including infant formula.

FDA scientists conducted two tests of the formula sample, one finding a melamine level of 137 parts per billion (ppb) and another measuring 140 ppb. A level of 250 ppb or less is considered a trace amount, Leon said.

But some consumer advocates said it was premature to say there was no risk for infants.

The FDA's earlier determination that 250 ppb of melamine was a trace amount was intended for foods other than infant formula, said Sonya Lunder, a senior analyst with the Environmental Working Group.

(Agencies via China Daily November 28, 2008)