Police have launched a criminal investigation into the death of a baby who contracted an infection from a suspected contaminated drip.
Officers from the Metropolitan Police's Homicide and Major Crime Command are investigating the death at Guy's and St Thomas' NHS Foundation Trust in London on 1 June.
They also "investigating the circumstances" of a second baby who died at the same hospital on June 10.
A Metropolitan Police spokesman said: "The current focus of this investigation is on the production of intravenous feeds."
Scotland Yard said officers have liaised with police in Cambridgeshire about a third baby who died in similar circumstances at the Rosie Maternity Hospital in Cambridge.
The families of the babies have been notified of the investigation by police, the force added.
A Met police spokesman said: "We are not investigating the health trusts.
"The MPS is working with a number of agencies to progress matters.
"We are aware of a small number of other babies who received this feed and are working with relevant agencies to speak to those families."
The deaths were linked to a batch of total parenteral nutrition (TPN), which is supposed to deliver a variety of nutrients intravenously when a baby is unable to eat on its own.
Public Health England (PHE) and the Medicines and Healthcare products Regulatory Agency (MHRA) launched an investigation in June into the blood poisoning of up to 23 babies who were given the feed, including three deaths.
The youngsters were thought to have developed septicaemia after being infected with the bacillus cereus bacteria.
Officials were investigating 19 confirmed cases and four probable cases at 11 NHS organisations in England.
One of the youngsters who died at St Thomas' Hospital was named as nine-day-old Yousef Al-Kharboush.
Speaking after a pre-inquest review in June, his father Raaid Hassan Sakkijha said: “Everyone who has a child will understand what a father feels like in a case like this, with suffering before your eyes.”
ITH Pharma, who supplied the intravenous fluid, said at the time that the suspected contamination has been traced to a “sourced” single raw material ingredient.
The London-based pharmaceutical company was not drawn on details of the material it received from one of its suppliers.