Staff are carrying out a 'deep' clean at Belfast's Royal Maternity Hospital neonatal room after an bacterial infection killed three babies.
The infants died over a two-week period this month after they contracted the Pseudomonas infection.
The neonatal room at the hospital has been emptied and is being cleaned over the weekend.
Northern Ireland Health Minister Edwin Poots said that a team of specialists is trying to identify the source of the infection.
Mr Poots said this evening that three other babies had picked up the infection.
It has earlier been reported that four babies had contracted the infection.
Mr Poots said there is no need to transfer expectant mothers to the Republic and that every action is being taken to minimise the spread of infection.
He added: "I fully understand the anxiety of parents and the wider community, however, we are doing everything we can to ensure safe continuity of care for the babies, and support for their families."
A different and apparently unlinked strain of the infection also claimed the life of another baby in Altnagelvin hospital in Derry last month, health officials said.
