NHS Grampian, the publicly funded healthcare system, said infection-control specialists were investigating two confirmed cases and four suspected cases of E. coli 0157 among children who attend Rose Lodge Nursery School in Aboyne, The Scotsman reported.
The baby unit at the nursery school has been closed but the nursery remains open.
Forty children, ages 6 weeks to 5 years old, attend the nursery school.
NHS Grampian said an investigation to try to determine the source of the potentially deadly E. coli extended beyond the nursery in the predominantly rural area.
The last significant outbreak of E. coli in Scotland came in 2002, when four members of a family from Oldmeldrum died of the infection, The Scotsman said.
An NHS Grampian spokeswoman said E. coli 0157 bacteria are commonly carried by farm animals.
Julie Grant, the owner of the nursery, said in a statement, "The nursery has a high standard of hygiene and rigorous infection-control procedures."