The seven victims of the Omagh fire tragedy all died from smoke inhalation, police revealed today.
Police forensic experts examine the burnt shell of a house destroyed by a fire in Omagh, Co Tyrone.
It is understood a post-mortem examination found no evidence that any of the five children were dead before the fire started.
As part of their investigation police were seeking clues that they had been stabbed or drugged but there was nothing to suggest that.
Authoritative sources also insisted today that Arthur McElhill's partner Lorraine McGovern was not pregnant.
Mr McElhillremains a key suspect even though police have yet to formally identify anybody because of the intensity of the blaze, with experts reduced to using DNA tests on the remains.
They are treating it as a murder investigation and all lines of inquiry are open. Independent councillor Paddy Magowan said: "If there was no one external involved in it then it doesn't ease the pain anymore for the relatives.
"Certainly it is a very painful situation, fire takes many angles, but smoke inhalation is very dangerous."
Witnesses described watching helplessly as the parents attempted to smash an upstairs bedroom window before they were overcome and the house exploded like a bonfire.
St Conor's primary school, next door to the Lammy Crescent scene in the Co Tyrone town, reopened yesterday. Children Sean, seven, and Bellina, four, were pupils.
A prayer vigil was held as the remains were removed. The eldest of the children, Caroline, 13, attended the nearby Sacred Heart College.
A PSNI spokeswoman said: "The post-mortem examinations of all seven bodies has been completed. The results indicate that the initial cause of death was smoke inhalation.
"Police inquiries will be continuing." The remains were removed from the charred rubble on Thursday after days spent combing the area for forensic clues.
Detectives launched a murder investigation after petrol was discovered inside the house.