At least 11 children aged between one and five are being treated in hospitals across Scotland for paediatric hepatitis.
There is no clear connection between the cases but Public Heath Scotland (PHS) has launched an investigation into the cause.
The agency is warning parents to check young children for signs of jaundice.
The youngsters affected are in four Scottish health board areas, namely Glasgow, Lanarkshire, Tayside and Fife, with most cases having arisen from March.
All of the children are being treated at hospitals in Edinburgh and Glasgow.
Dr Nicholas Phin, director of public health for Public Health Scotland, said: “If you have a child who is showing signs of jaundice, where the skin has a yellow tinge and is most easily seen in the whites of the eyes, then parents should contact their GP or other health care professional.
“We are continuing to investigate these cases and will provide further updates as and when they are available.”
The hepatitis viruses commonly associated with this condition have been excluded, according to PHS. Each year, around seven or eight cases of non-A to E hepatitis are detected in children in Scotland.
PHS said the number of cases in such a short period of time, combined with the geographical spread and severity of illness – in some cases – is unusual and requires further investigation.
All potential causes are being explored but infection is considered to be a more probable source at this time.
Investigations are still in the early stages and PHS is working with partners and other agencies across the UK to investigate the cases.
A Scottish Government spokesman said that the 11 cases discovered, which presented as an inflammation of the liver, were “termed as being non A to E hepatitis as they are not explained by the usual hepatitis viruses”.
He added: “All potential causes are being investigated and the Scottish Government will continue to closely monitor the situation along with PHS and other health protection agencies.”