Public Health England (PHE) today said health officials had identified three further cases, bringing the total number to 21.
The cases were identified after analysis of clinical records of the babies, a spokeswoman said.
The latest probable cases were identified at Stoke Mandeville Hospital in Buckinghamshire, Chelsea and Westminster NHS Trust in London, and Addenbrooke's Hospital in Cambridge.
The babies are responding well to treatment.
A baby has died at Addenbrooke's Hospital in Cambridge after being fed a suspected contaminated drip feed.
Public Health England has announced that a baby has died and 14 others have been infected in an outbreak of blood poisoning in hospitals.