A two-year-old girl has died and another two children became ill after contracting E. coli 0157. Ellie Russell, from Ballantrae, South Ayrshire, died on Saturday after being taken to the Royal Hospital for Sick Children in Glasgow.
Two other children from the Dumfries and Galloway area, whose family had contact with Ellie, have also tested positive for E. coli.
The children, aged one and three, were admitted to Dumfries and Galloway Royal Infirmary at the weekend but have since been discharged.
Carol Davidson, director of public health at NHS Ayrshire and Arran, said: "Investigations into the source of the infection are ongoing, but at the moment we have no reason to believe that others outside the families affected and their contacts are at any increased risk."
E. coli 0157 can be spread by eating contaminated food or not washing hands after contact with farm animals. Symptoms can include diarrhoea, nausea, vomiting, stomach pain and fever.