Three babies died after contracting a waterborne bacterial infection at a hospital in Danville, Pennsylvania, CBS Scranton affiliate WYOU-TV reports. Five others were infected in the neonatal intensive care unit at Geisinger Medical Center; four have recovered while one is still being treated.

The cases of pseudomonas infection were contained in the NICU and have not been reported in other parts of the hospital. According to a statement from Geisinger Medical Center, the facility is working with state health department officials as well as the Centers for Disease Control and Prevention to investigate and eradicate the bacteria.

"Out of an abundance of caution, the obstetrics and neonatal teams at Geisinger Medical Center are temporarily diverting mothers likely to deliver prematurely before 32 weeks gestation, and infants born at less than 32 weeks gestation, to other regional institutions," the hospital said in a statement.

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The bacteria are common and often harmless but can cause disease in "very fragile patients," Dr. Frank Maffei, the hospital's chair of pediatrics, said at a news conference.

The deaths, he said, "may have been a result of the infection complicating an already vulnerable state."

Doctors said they first became aware of an unusual infection in early August.

The neonatal intensive care unit is inside a children's hospital that is part of a larger campus. It could take weeks to determine how the infections occurred, although it's likely the pathogen was brought in from outside the children's hospital, investigators said.

"It's really too soon to say exactly where the organism is coming from, but the information we have so far suggests that it's someplace outside of the neonatal intensive care unit," said Dr. Mark Shelly, Geisinger's director of infection control and prevention.

The hospital has increased chlorination of water, bolstered water filtering, performed extra cleaning and changed some of its processes.

The investigation may not reveal exactly what went wrong, Shelly said.

Seven of the eight babies were born at less than 26 weeks of gestation, and the eighth was born at less than 27 weeks', according to the hospital.

The Danville hospital's neonatal intensive care unit treats more than 600 babies a year.