Gardaí say it could be up to a week before the results of toxicology tests from three children found dead at their home in west Dublin last Friday night are known.
And detectives may have to wait some time before their mother, Deirdre Morley, who is in a serious condition in hospital, is physically and psychologically capable of talking to them.
The bodies of Conor, aged nine, Darragh, aged seven, and their three-year-old sister, Carla, were discovered in the house in Newcastle by their father, Andrew McGinley, when he arrived home at around 7.45pm.
There were no obvious injuries on the children and a post mortem was not conclusive in determining the cause of death.
Toxicology tests are being carried out on the children to determine whether or not they had consumed any substances and what role they might have played in their deaths.
Sources said that while the results could be back in a matter of days the results of a “broad spectrum analysis” could take a week or so.
Ms Morley was found by a taxi driver at around 7.30pm walking near her home in a disorientated state.
Concerned for her safety, the driver took her home, but on arrival her condition had deteriorated and he rang emergency services.
A garda patrol car happened to be in the area responding to a separate matter when they saw ambulance staff tending to a person and went to see if any assistance was needed.
At that stage, Mr McGinley had arrived home. It is understood that when he discovered his wife was being cared for outside the house he went inside to see if the children were okay.
When gardaí heard the father's anguish they immediately went into the house, followed by paramedics.
It is understood one of the children was in a downstairs room and the two others upstairs.
It is understood that two notes were found inside the house, one of them immediately inside the door, asking that people ring 999 and not to go upstairs. Both notes are being forensically examined.
The Technical Bureau has conducted a detailed examination of the house.
Ms McGinley, a nurse, was brought to Tallaght Hospital and was described as being in a critical condition on admittance.
She is thought to have stabilised over the weekend, but is still in a serious condition.
Detectives will have to wait until doctors assess that she is able to talk to them before they can ask her about that day.
Sources said doctors will need to be satisfied that she is both medically and psychologically able to speak to gardaí before giving detectives the all-clear.
Gardaí have been working very closely with Mr McGinley.
A family liaison officer had been appointed and is in contact with the father and the extended family.
House to house inquiries are being conducted in the estate.
It is understood the children had attended school or creche as normal on Friday before returning home that afternoon.
Conor and Darragh were in third and first class respectively in a local gaelscoil in Rathcoole, while Carla attended a pre-school.
The garda investigation team is trying to determine when the children were collected, what were their movements after that and when they were last seen alive.
An Garda Síochána is liaising closely with South Dublin Children and Young People's Service Committee (CYPSC) to provide supports through schools, counselling services, family services, local groups etc to support children and families through the days, weeks and months ahead.