A child being treated for an acute form of hepatitis in the Republic of Ireland has died, the Health Service Executive has said.
A second child also being treated for the illness has received a liver transplant.
Both cases are being linked to an unexplained type of hepatitis being reported in children across the world.
The European Centre for Disease Prevention and Control has said the total number of cases reported worldwide is about 450.
An alert about the disease in children was first raised by the UK in early April.
It has since been identified in dozens of countries.
The HSE said over the past two months, six probable cases of children with hepatitis of unknown cause have been detected in Ireland.
They were aged between one and 12. All were hospitalised.
In addition, a small number of other cases are being assessed to see if they are linked to the acute hepatitis of unknown origin or if they have another cause for their illness.
The HSE said the cause of the disease in those children has not yet been found and all possibilities are being investigated.
A possible link to an increase in infections caused by adenovirus, a common cause of childhood illness, is being investigated.
Other possible causes such as other infections – including Covid-19 – or something in the environment, are also being investigated.
Investigations are under way to determine if current or prior Covid-19 infection may increase the risk of this disease in some children.
None of the Irish cases who were tested on admission to hospital had evidence of Covid infection at that time.
The majority of the cases had not received Covid-19 vaccination.
