The hospital said it changed the breast milk preparation procedure on Sept. 30 to “single-use equipment to measure and administer donor breast milk.”

“We have had no new cases of infants becoming ill from pseudomonas in the NICU since making this change,” Dr. Hartle said, emphasizing that “the donor breast milk at Geisinger is safe and we are certain the milk itself was not the cause of the exposure.”

The hospital, which was already diverting care of some premature babies to other local hospitals while it investigated the infections, said that it was continuing to divert mothers “delivering at less than 32 weeks and babies born prematurely at less than 32 weeks” while it consulted with the health authorities about resuming normal operations.

At least one of the families whose child died has filed a lawsuit against the hospital. Matt Casey, a lawyer representing two out of the three families whose infants died, said the hospital’s statement “raises more questions than it answers.”

“They haven’t told these families anything about the details of when they knew about this, and what they did about it prior to their babies being admitted to that NICU,” he said.

Abel Cepeda was born to Mr. Casey’s clients, Zuleyka Rodriguez and Luis David Cepeda, of Hazle Township, Pa., on Sept. 24. He died on Sept. 30, the same day that the breast milk process was changed.

“His parents were told that they didn’t know why he died,” Mr. Casey said.

A day before the October news conference in which the infections were announced, the parents got a call telling them the cause of their baby’s death was a bacterial infection, he said.