The Food and Drug Administration, the Centers for Disease Control and Prevention and state health departments are still investigating the four recent cases of Cronobacter infection in infants in Florida, Illinois, Missouri and Oklahoma, according to a CDC statement issued Friday.

The CDC said that there was still no evidence to suggest that the four bacterial infections in infants were related and parents may continue to use powdered infant formula.

The joint investigation is ongoing and includes laboratory testing of various types and brands of powdered infant formula, nursery water, and available clinical samples from infants, according to the CDC.

The investigation also looks into the manufacturing facilities for infant formula and nursery water.

A DNA fingerprinting test of the bacteria from the two recent cases of Cronobacter infection in Missouri and Illinois show that the bacteria were genetically different, and suggests they are not related.

Test samples provided by the Missouri Department of Health and Senior services found Cronobacter bacteria in an opened container of infant formula, an opened bottle of nursery water and in a prepared infant formula, but investigators are still unclear as to how the contamination occurred, CDC said.

FDA tested factory sealed containers of powdered infant formula and nursery water with the same lot numbers as the contaminated opened containers collected from Missouri and found no trace of Cronobacter bacteria.

The CDC stated that there is currently no evidence to suggest that the infant formula or nursery water was contaminated during manufacturing or shipping, and the results of the environmental samples related to the ill infants from Illinois and Oklahoma are still pending.

Last month, after the infection of infants from Missouri and Illinois, the CDC had asked federal health officials around the country to look for other cases of Cronobacter infection among infants which resulted in two additional cases in Oklahoma and Florida. 

The infants from Missouri and Florida died as a result of the infection, while the infants from Illinois and Oklahoma survived, the CDC reported.

The CDC said that cronobacter bacteria is found in the environment and in hospitals and homes, and can be multiplied in a powdered infant formula after the powder is mixed with water.

The health organization emphasized that mothers should breastfeed whenever possible and offer a few safety recommendations on how to prepare and use powdered infant formula:

- Wash hands with soap and water before preparing the formula

- Thoroughly clean all feeding equipment with hot, soapy eater

- Prepare just enough formula for one feeing at a time, and give it to the baby right away.

- Follow the directions on the printed label