A car fire, which left two children dead and their mother seriously injured, may have been started maliciously.
The two-year-old boy and five-year-old girl were discovered in Multyfarnham on Friday at around 4pm.
They have been named as Michael (2) and Thelma (5) Dennany.
A woman aged in her 40s, their mother Lynn Egar, was taken from the scene by air ambulance to a Dublin hospital.
She continues to be treated for serious but non-life threatening injuries.
A forensic examination of the vehicle by the Garda Technical Bureau has taken place, while post mortems have been carried out on the bodies of the two children.
The family home in Rathowen has also been sealed off and undergone an examination.
Conor Lally is security and crime editor for The Irish Times.
He told Newstalk Breakfast passersby were already trying to help when emergency services arrived.
"A driver had actually stopped in the area, and he had tried to rescue Lynn Egar and her two children.
"So Lynn Egar and the young boy were actually out of the vehicle when Gardaí arrived.
"But unfortunately Thelma was effectively trapped in the car, and her remains were found in the vehicle when the blaze was brought under control.
"The enquiry is still in its relatively early stages now - but based on the evidence gathered so far, Gardaí believe that the fire was started as a result of an arson attack.
"So the enquiry is a criminal enquiry at the moment, and they're just trying to find out exactly what happened and who was involved", he said.
An Garda Síochána continue to appeal to any person with information to contact them.
An incident room at Mullingar can be contacted on 044-938-4000, the Garda Confidential Line at 1800-666-111 or any Garda station.
A family liaison officer is continuing to keep the family updated, while the results of the post mortem examinations are not being released for "operational reasons."