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.