A Perthshire nursery school is at the centre of a three-day deep clean after a suspected case of E-coli was detected.
Health bosses say suspected symptoms were detected in a child with links to Errol nursery and stressed the risks to the wider public were very low.
NHS Tayside and Perth and Kinross Council are investigating how the infection may have come about.
The school remained open while the nursery area was cleaned thoroughly overnight on the advice of public health experts. Council chiefs insisted the operation by Tayside Contracts was being carried out as a precaution.
The health board wrote to parents last week to say experts were investigating a single case of suspected Escherichia coli, more commonly known as E. coli.
The germs are commonly found in farm animals and can cause sickness, diarrhoea and a fever in humans.
An NHS Tayside spokeswoman confirmed yesterday the infection was in a nursery pupil and that investigations are ongoing.
She said: “NHS Tayside’s health protection team is aware of and currently investigating a single suspected case of E. coli non O157 infection in a child who attends a nursery in Perthshire.
“As a precaution, a letter has been issued to parents of children at the nursery for information and reassurance.
“The risk to the wider public is very low.”
The statement was backed by the local authority, which said the source was believed to have come from outside the nursery.
A spokeswoman said: “Perth and Kinross Council has been informed of a single possible case of suspected E. coli at Errol Nursery, for which the source is a third party outwith the nursery.
“Following guidance from Public Health, Tayside Contracts is conducting a three-day deep clean of the nursery areas as a precautionary measure.”
Some strains of E.coli are harmless but others can cause illness, with young people and the elderly most at risk.
It can be caught by consuming contaminated food or water, or through contact with a person or animal carrying the infection.
Advice to avoid catching the virus includes thorough hand washing, especially after handling raw meat or handling animals, as well as preventing cross-contamination of raw and cooked meat.