A group of parents will meet the Eastern Regional Health Authority this week to find out why their children's brains were retained without permission, after a road accident in 1998.
Mr John Byrne and Mrs Mary Byrne lost their daughters Fionnuala (21) and Sharon (24) in the crash between a minibus and a lorry, outside Arklow, Co Wicklow. They were accompanying children to a special needs unit in Newcastle. The bus driver and two young boys also died.
Three weeks ago the Byrnes' GP confirmed that their daughters' brains had been retained after the coroner's post-mortem in St Columcille's Hospital in Co Dublin without their knowledge.
The brains had then been sent to another hospital but the parents have been unable to discover which hospital received them and why. "All we know is that the organs have been disposed of since," Mrs Mary Byrne said. The boys' parents also learned that their sons' organs were sent to another hospital.
A spokeswoman for the health authority said organs were removed and sent to another hospital for further examination by a neuropathologist to determine the cause of death. She said the hospital had not informed the parents as it feared it might have caused them further distress.
"It's like a bereavement all over again," said Mrs Byrne. "It happened nearly three years ago, but it brings it back again."
The ERHA spokeswoman said it was now trying to get definitive information.
"We deeply regret the distress which the families concerned have suffered," she said. "We are anxious to alleviate this in any way possible and to co-operate fully with the families in providing all information."
