Three babies have died at the Royal Maternity Hospital in Belfast after an outbreak of pseudomonas.
The bacteria can cause infections in the chest, blood, and urine.
The ward where the babies were being treated was closed at the weekend as it underwent a deep cleaning, this as hospital authorities tried to identify the source of the infection.
The babies died in the last two weeks, but a possible link to the bacteria was only discovered in recent days.
There were 26 babies in the unit, which cares for ill or premature newborns.
In a statement, the Belfast Trust, which runs the hospital, said: "To help prevent the spread of this infection everyone including parents and guardians are being asked to be diligent in their hand hygiene when entering and leaving the unit. The situation will be kept under constant review."
