A baby at the Whittington Hospital is among several diagnosed with blood poisoning after being given what appears to be a batch of contaminated food.
One baby has died and a total of 14 others at neonatal units in six hospitals across the region are reported to have been affected by the liquid batch.
Those affected, many of whom were premature, were fed the liquid food directly into their bloodstream as they could not be fed orally.
Public Health England and the Medicines and Healthcare Products Regulatory Agency are investigating but say they do not expect any more cases.
They said the surviving babies are responding to antibiotics and that they believe they have identified the source of the contamination.