Babies have been evacuated from a neonatal room at a hospital in Northern Ireland after three died from an infection, medical staff said.
A bacteria called pseudomonas caused the deaths at the Royal Maternity Hospital in Belfast, and other vulnerable babies have been swabbed for signs of it.
The area where they were being treated will undergo deep- cleaning after the remaining three patients have been moved.
A helpline has been established for worried relatives.
The bacteria can cause infections in the chest, blood and urinary tract.
Consultant Clifford Mayes said: "Where it is possible, we will transfer a mother and baby out before delivery to other hospitals.
"The large area with 13 babies is being deep-cleaned. There are only three babies remaining in that room."
Pseudomonas is not itself infectious but because it exists in water or moisture patients can carry it on their skin. It can be treated with the right antibiotic but the third baby died despite the treatment.
The unit is populated by extremely premature and small infants.
Belfast Health and Social Care Trust chief executive Colm Donaghy said they would be carrying out a full investigation into whether anything else could have been done.
Dr Mayes said the first death happened on January 6 and the second on January 13. The third infant died late last night.
"Every baby has been screened with skin swabs, looking for any evidence of pseudomonas," he said.
"It is a germ which can be on your skin and not cause any harm but with a sick patient it can cause very serious problems.
"The babies now are being moved depending on results as they come back."
A large intensive care room which can take up to 13 babies will be cleared within the next few hours.
The infants are being separated into small rooms and the deep- clean will be carried out over the weekend.
Dr Mayes said it would be some time before other information about the outbreak was collated. Blood samples take 48 hours to be analysed.
Doctors first became aware that there was a problem with the infection on Monday night when the laboratories reported.
Some babies may be moved to other health trusts or even outside Northern Ireland if the pressure becomes too great.
It will take at least a week to find out if there were deaths relating to different strains of the infection. Usually there are fewer than 80 cases of it annually across Northern Ireland.
Health Minister Edwin Poots said the authorities were taking the matter very seriously.
"It is important that we remain calm. Infection control teams are now in the process of trying to identify the source of the infection and minimise the risk of spread to other babies in the unit," he said.