Another suspected case of a baby being infected by a killer bacteria is under investigation by medical staff at the Royal Jubilee Hospital in Belfast.
The source of the outbreak, which has already claimed the lives of three infants, has still to be identified.
Laboratory tests have not confirmed another case, but the victim is understood to be suffering from the same Pseudomonas symptoms.
Six other babies have traces of the bacterial infection on their skin. They are being closely monitored to make sure it does not enter their bloodstream.
A major deep clean of the maternity unit has been carried out, but staff have been unable to trace the source of the infection. Taps were removed and sinks and pipes checked amid fears it could be in the water system.
Northern Ireland health minister Edwin Poots is expected to get a new report on Tuesday and make a full statement to the Assembly.
He said: "We can't suggest at this stage that's the cause of the problem, but it's certainly one of the areas being investigated."
The first baby died on January 6, the second a week later and the third last Thursday night.
Pseudomonas aeruginosa can be found in soil and stagnant water. The children who died were born prematurely. The disease can also pose a threat to elderly people with weak immune systems.
The Department of Health has confirmed that the number of babies who have bacteria on their skin is now six. A statement said: "It is not causing active infection in these babies. The babies continue to receive the neonatal care they require. As a precautionary measure, babies' skin may be screened again as the situation requires to see if they are carrying the bacteria."