CHEVERLY, Md. – The neonatal intensive care unit at Prince George’s Hospital Center was temporarily shut down Tuesday after the discovery of potentially deadly bacteria in nasal swabs of three infant patients, hospital officials said.

Nine babies were being transferred from the hospital in Cheverly, Maryland, to the NICU at Children’s National Medical Center in Washington, D.C., “out of an abundance of caution,” said Delores Butler, a spokeswoman for Dimensions Healthcare Systems, the nonprofit entity that runs hospitals in Prince George’s County, Maryland.

Those transfers were expected to be completed by Tuesday night.

Hospital officials emphasized that the babies who tested positive for the pseudomonas bacteria have not shown any symptoms of illness from that infection, which can be mild in healthy individuals but far more serious for those with compromised or immature immune systems.

Dimensions board members were notified by phone Sunday about the presence of what hospital officials are describing as a troubling “cluster” of the bacteria among the NICU patients, according to two individuals with direct knowledge of the phone calls.

The discovery of the bacteria followed two recent deaths in the neonatal unit, said the two people, who spoke on the condition of anonymity because they were not authorized to comment to reporters. They also said the bacteria were found in water pipes near the NICU.

Hospital officials said that the cause of the two infant deaths was still being investigated and that so far there was no evidence that the deaths were related to the presence of the bacteria.

“There have been no clear deaths associated with these infections,” said Carnell Cooper, chief medical officer for the hospital center. He added that neonatal patients suffer from “a number of conditions that put them at risk to die.”

Cooper declined to provide details on the infants’ deaths, which along with the presence of the bacteria, were first reported by WJLA (Channel 7).

He said the hospital routinely swabs the nostrils of infants in the NICU to survey the amount and types of bacteria on their skin. When those tests showed pseudonomas in more than one baby, the hospital notified state health officials, who suggested moving the infants.

Hospital officials are now working backward to determine how long the bacteria may have been present in the NICU and how they were was introduced.

The hospital stopped admitting neonatal patients Thursday and also stopped using tap water in the intensive care unit at that point.

Joan Hebden, a nurse specializing in infection prevention with the University of Maryland Medical School, said the hospital has contracted with a company to collect samples and analyze the water to determine where the bacteria is coming from.