Gardaí believe the house fire in Dundalk, which claimed the lives of two little girls and their father, started accidentally.
The most likely causes were an electrical fault, a cigarette or a chip pan, said a Garda source.
The funerals will take place this morning of Mr Eddie Walls (39) and his daughters, Teresa (three) and 18-month-old Natasha. Thousands of mourners are expected to attend.
Yesterday, the uncle of Eddie Walls, Mr Eamonn Walls, said his nephew was a doting father who lived for his children.
"I have never seen a man go on so much about his children, you would expect it from women but he spoke and thought of nothing else."
Such was his devotion that he and his wife Michelle (24) had already bought their Christmas presents and hidden them in the attic until Christmas morning.
The house in Castle Ross, Dundalk, was destroyed by the fire, which broke out sometime after 1 a.m on Sunday.
The children's mother managed to escape but, said Mr Eamonn Walls, "she is shattered. It just doesn't make sense to her; she is absolutely devastated. The whole family, which is close knit, has been devastated."
During the hours after the fire, members of the family were contacted individually by gardaí and told the news.
They had spent the previous day celebrating Eddie's 39th birthday and later on, he and his wife joined their next-door neighbours at a party for the christening of the neighbour's daughter.
Mr Walls worked as a painter and decorator. His uncle said: "He worked hard and did everything for his wife and children."
The couple met five years ago and married in Mr Walls's parish of the Holy Redeemer, which is a short distance from where they lived.
His father, Stephen, who also lives nearby, was too upset to talk to the press about the loss of his son and his two granddaughters.
The family praised the efforts of the neighbours in Castle Ross, who made valiant efforts to try and rescue Mr Walls and his daughters.
Mr Eamonn Walls said: "I think we have to comment on their efforts. I have heard of one man who got his television and threw it through a window. As a result of his efforts he injured himself. These efforts by the Castle Ross community are a tremendous help to us and say a lot about the type of people they are. It is at times like this you realise how good people are."