Gardaí in Co. Kildare have launched a triple-murder investigation into the deaths of three people 30 years ago.
Officers investigating a fire on Church Lane in Kilcock, Co Kildare, in 1987 had originally believed the blaze was an accident.
Three-year-old Kerrie Ann Byrne, eight-year-old Mary Ellen Byrne and their auntie Barbara Doyle, aged 20, who was babysitting them on the night died in the house fire in September 1987.
The Serious Crime Review Team and detectives at Leixlip Garda Station got new information that the fire was started on purpose.
Chief Superintendent Gerard Roche said it comes after "new evidence" came to light quite recently.
He said: "The investigation remained open since this time. New evidence has come into our possession and we now believe that the fire was started deliberately.
"The investigation has now been upgraded to a murder investigation. We are satisfied that there are people who will remember this fire and the deaths of Barbara, Mary Ellen and Kerrie, and who have not spoken to the gardaí."
"We are appealing to any person who has any information to contact Leixlip garda station at 01-6667800 or the Garda Confidential Line 1800 666 111. I would further appeal that the privacy of the Byrne and Doyle families is respected at this time."
On the night of the fire the children's parents Aidan (now dead) and Elizabeth, went to a 21st party in the area.
Their mother still lives in the house and the family have been informed of the murder probe.