A likely contamination of liquid food was blamed for the death in Britain of one baby and the poisoning of 14 more, regulators said.
The one fatality occurred at London's Guy's and St Thomas' Hospital, while the other babies - many premature - are said to be responding to antibiotic treatment in six hospitals across England.
The food was administered via liquid feed as the babies were unable to mouth feed.
Public Health England and the Medicines and Healthcare products Regulatory Agency said a bacterium known as Bacillus cereus was to blame.
An alert has been issued to recall a batch - manufactured by ITH Pharma Limited - that expired on Monday.
"Investigations with the company have identified an incident that might have caused contamination," the two organisations said in a statement.
Karen Hamling, managing director of ITH Pharma, said the firm was helping investigators.
"ITH Pharma is very saddened to hear about the death of a baby in hospital," she explained.
"The products in question, which are no longer in circulation, are made to order for individual patients on a daily basis, in response to bespoke orders from hospitals.
"We are co-operating fully with the MHRA in the investigation, and are doing everything we can to help them establish the facts in this case as quickly as possible."