KANSAS CITY, Mo. – Four cases of infants sickened by a rare bacteria sometimes linked to powdered formula, including two who died, are not related, and parents can continue using the products to feed their babies, two federal agencies announced Friday.

Scientists with the Centers for Disease Control and Prevention and the Food and Drug Administration tested various types of powdered infant formula and distilled water, known as nursing water, and found no cases of contamination by Cronobacter sakazakii.

Four babies, including one in Missouri and another in Florida who died, were sickened by the bacteria that are found naturally in the environment and in plants such as wheat and rice. Cronobacter also has been traced to dried milk and powdered formula.

Two other babies, in Illinois and Oklahoma, were sickened by the bacteria but survived.

The Missouri baby, Avery Cornett of Lebanon, Mo., died in December after appearing lethargic and displaying what his family said were signs of a stomach ache. Tests at a Springfield hospital showed he had Cronobacter, and he died a few days later.

Several national retailers pulled Enfamil Newborn formula, which Avery had consumed before getting sick, from 3,000 stores until the batches could be tested. Those tests came back negative, the CDC said Friday.