Our Lady's Children's Hospital, Crumlin has apologised to 18 families who were wrongly identified as being at the centre of a contamination scare over a medical scope.
In a statement the hospital said that seven new patients, separate from the 18 who have now been given the all-clear, are now being contacted about the colonoscope contamination.
Speaking on RTÉ's Morning Ireland, Dr Colm Costigan, Clinical Director of the three Dublin paediatric hospitals, apologised for the distress caused to families.
He said: "It appears what happened was that when we did the quality assurance check on our scopes back on 6 July, there were two scopes that didn't pass the test and was contaminated with ESBL (extended-spectrum beta-lactamases).
"Unfortunately, there seems to have been an error in that the contamination was attributed to the wrong scope."
Dr Costigan said he personally contacted the original 18 families last night to reassure them they were not affected by the contaminated scope.
The hospital said it has contacted all seven other families who are now affected.
Dr Costigan said a "look back" investigation was under way to try to find out what happened and also why the wrong colonoscope was identified as being contaminated.
The hospital said an information pack and testing kit would be sent to the seven families. It said families would be notified immediately of the results.
The contamination problem involves children who underwent a colonoscopy with a contaminated colonoscope between 17 May and 5 July.
The problem emerged when a crack was found in the colonoscope and tests on 6 July last showed the crack contained a bug that can cause infection and cannot be cleared by antibiotics, but can be treated.
Elsewhere, HSE Director General Tony O'Brien said he has asked a senior official in the HSE to report into how the incorrect information was given to the 18 parents.
Mr O'Brien described the handling of the issue as a "catastrophic failure of the incident management process".
He said the "root cause analysis" would be carried out by the HSE's National Director of Quality and Patient Safety.
The review will examine how the misinformation occurred.