Despite its earlier statement about not being able to determine a threshold for the safe amount of certain toxic chemicals in infant formula, the Food and Drug Administration officials defended the US-manufactured formula on Friday, saying that the trace amounts are safe.

In spite of the tests that found the chemical melamine in one brand and a related compound - cyanuric acid - in another, Stephen Sundlof, director of the FDA's Center for Food Safety and Applied Nutrition, said the amounts found are far less than levels found in infant formula in China earlier this year, and "do not raise public health concerns. The domestic supply of infant formula is safe."

The agency said it had determined that levels of melamine, or one of its related compounds, below 1 part per million in the infant formula, were not an issue of concern.

During a conference call, Sundlof said FDA tests found "very low levels" of the industrial chemical melamine in Nestle's Good Start Supreme with Iron formula. Similarly, low levels of cyanuric acid were found in Bristol-Myers Squibb unit Mead Johnson's Enfamil Lipil with Iron.

Specifically, the FDA said that among the 74 final test results discussed Friday, two samples of Nestle's formula tested positive for melamine at levels of 137 and 140 parts per billion, well below the level of concern cited by Sundlof. The agency has 13 more samples to test.

Meanwhile, the Xinhua news agency reported on Friday that China's quality watchdog said it was seeking more information from its US counterpart on US-made infant formula on sale in China.