The Food and Drug Administration said Tuesday that it had discovered the toxic chemical melamine in infant formula made by an American manufacturer, raising the possibility that the problem was more extensive in the United States than previously thought.
While few details were available late Tuesday, agency officials said they had discovered melamine at trace levels in a single sample of infant formula. It was also discovered in several samples of dietary supplements that are made by some of the same manufacturers who make formula.
F.D.A. officials insisted that the levels of melamine were so low that they did not pose a health threat.
“There’s no cause for concern or no risk from these levels,” said Judy Leon, an agency spokeswoman. Ms. Leon said the contamination was most likely the result of food contact with something like a can liner, or from some other manufacturing problems, but not from deliberate adulteration.
She declined to name the company that made the tainted infant formula.
Melamine contamination became a major scandal in China after it was added to milk to disguise test results that measure protein levels. Since it was discovered in infant formula in September, it has sickened more than 50,000 infants and killed 4.
The F.D.A. has beefed up its inspections of Asian markets to make sure that infant formula and other products from China are not contaminated with melamine. At the same time, the agency said it had received assurances from American infant formula manufacturers that they did not import ingredients from China.
To date, several products carried primarily by Asian markets have been recalled because of melamine contamination, including certain varieties of Mr. Brown instant coffee and tea, White Rabbit Creamy Candy and Blue Cat Flavor Drink. Two weeks ago, the F.D.A. said all Chinese products containing dairy ingredients would be stopped at the border until importers proved they were not contaminated.
Though manufacturers of domestic infant formula say they do not use Chinese ingredients, the F.D.A. began sampling infant formula anyway, using more sophisticated testing than had previously been available.
Ms. Leon said the agency was testing 87 samples and had completed all but 10 of the tests. Of those, only one contained traces of melamine, she said. The F.D.A. allows anything below 250 parts per billion of melamine in infant formula, and the sample contained less than that, she said.
Ms. Leon said the other products containing trace elements of melamine were also below allowable levels. For supplements, the F.D.A. allows 2.5 parts per million, and she said all of the samples testing positive were below that figure.