( CNN ) -- After first saying that they could not determine a threshold for the safe amount of certain toxic chemicals in infant formula , Food and Drug Administration officials said Friday that trace amounts are safe . Worries over melamine in infant formula started in China and have spread to the United States . `` Amounts of the industrial chemical melamine or the melamine-like compound called cyanuric acid that are below 1.0 ppm [ 1,000 parts per billion ] do not raise public health concerns , '' said Stephen Sundlof , the FDA 's director of the Center for Food Safety and Applied Nutrition . When it became known in September that thousands of babies in China had been sickened by tainted infant formula , the FDA ordered the testing of U.S.-manufactured infant-formula products . Sundlof said Friday that results from 74 of 87 samples of infant formula and other products babies and young children had been completed . The results of the other 13 are pending . That total differed slightly from the one the FDA offered Thursday , when its acting commissioner of public affairs , Judy Leon , told CNN that 77 sample results had been completed and just 10 were outstanding . Among the 74 final test results discussed Friday , the FDA said , two samples of Nestle 's Good Start Supreme Infant Formula with Iron tested positive for melamine at levels of 137 and 140 parts per billion , well below the level of concern cited by Sundlof . In addition , three samples of Mead Johnson 's infant powder , Enfamil LIPIL with Iron , tested positive for cyanuric acid at an average of 247 parts per billion , also well below the FDA trace level . The FDA 's October 3 risk assessment of melamine and its analogues concluded that `` levels of melamine and its analogues below 2.5 ppm in foods other than infant formula do not raise public health concerns . '' But the agency said then that it did not have enough data to determine a safe level of melamine and its analogues in infant formula . On Friday , an FDA official said it was still not possible to determine a safe level for infant formula containing both melamine and cyanuric acid compounds , but officials `` believe that at very low levels there should not be any health concerns . '' Sundlof said the trace levels of melamine or related compounds detected in the samples are 10,000-fold less than the amount associated with Chinese infant-formula contamination . According to the World Health Organization , contaminated infant formula in China has killed four babies and caused more than 47,000 infants and children to be hospitalized with possible kidney stones . Chinese-made infant formula is not available in the United States , because no Chinese manufacturer meets the requirements to sell infant formula in this country , according to the FDA . It was also the combination of melamine and cyanuric acid in pet food that caused thousands of dogs and cats to be sickened last year in the United States . The combination caused crystals to form in the animals ' kidneys . According to the FDA 's updated Interim Safety Assessment , infants are more vulnerable to the combination than are older children or adults because formula could be the infants ' sole source of nutrition . In addition , their kidneys may not have developed sufficiently to ward off the impact of the chemicals .
FDA , cyanuric acid not of concern in levels below 1,000 parts per 1,000 . Official says Melamine has tested billion samples of U.S.-made baby formula . Some samples tested positive but at safe levels , official says . Levels are far below those associated with Chinese contamination .