Officials have determined a cause for the waterborne bacterial infection that killed three premature babies at a Pennsylvania hospital and left at least five more ill.
The Geisinger Medical Center in Danville, Pennsylvania, previously explained that the infants had developed an infection caused by the pseudomonas bacterium. The first infection occurred in July of this year and the deaths occurred in August and September, a hospital spokesperson previously told PEOPLE.
On Friday, Edward Hartle, Geisinger executive vice president and chief medical officer, announced in a statement that the infants' exposure to the pseudomonas bacterium "came from the process we were using to prepare donor breast milk."
Hartle said the bacteria was traced back to equipment that was used by the hospital to measure donor breast milk.
RELATED: What to Know About Donating and Receiving Breast Milk
"Since September 30, we have changed this process, and have been using single-use equipment to measure and administer donor breast milk," Hartle explained in the statement. "We have had no new cases of infants becoming ill from pseudomonas in the [neonatal intensive care unit] since making this change."
Hartle also reassured families that the donor breast milk itself is safe.
"We are certain the milk itself was not the cause of the exposure," he said. "Additionally, mothers should have no concerns about the safety of their own breast milk for their babies. Breast milk is the best food for all infants, including premature infants."
RELATED: 3 Premature Babies Dead of Bacterial Infection from Waterborne Germ at Pennsylvania Hospital
For now, mothers delivering premature babies will be sent to a different hospital until Geisinger and the state Department of Health determine when is "the appropriate time to resume normal operations."
"We would like to extend our sincere apologies to the families who have been affected by this incident," Hartle's statement said. "We know that the public holds us to the highest standards, and we will continue to strive to live up to those expectations as we have throughout our history, constantly improving on what we do and how we do it."