SAGUENAY, Que. - A suicide pact between a Quebec couple was at the root of a family tragedy that left the husband and their three children dead and the wife facing three counts of first-degree murder, police said Saturday.

The woman, only identified as the 36-year-old mother of the Laliberte clan, was recovering in hospital with an unspecified injury and will likely be charged Monday, said Sgt. Richard Gagne of the Quebec provincial police.

Gagne said police have determined Marc Laliberte, 46, and his wife planned to commit suicide after killing their three children.

Laliberte's body and those of the couple's three children were found early Friday in the family bungalow in Saguenay's Chicoutimi borough, about 250 kilometres north of Quebec City.

"The woman participated in the death of her three children and police placed her under arrest in her hospital bed," Gagne said.

"The woman has not been interrogated yet - but the analysis of the scene and the clues we've gathered have brought us to this conclusion."

Police would not speculate on a motive for the deaths and Gagne said he wouldn't get into what prompted the pact, but there have been reports the family was mired in financial trouble.

Marc Laliberte worked in real estate, but had recently been laid off from his job, according to reports - his profile had been removed from the website of a local realtor. A relative also confirmed the mother lost her retail job just before Christmas and that neither adult was working.

Gagne said police had met with many friends and relatives of the couple but there were still others they needed to interview.

Police said it was the mother who called 911 asking for help just before midnight Thursday.

Officers who answered the call found her wounded inside the home, and made the grisly discovery of the other bodies in the house.

Autopsies on the children - 12-year-old daughter Joelle; and sons Marc-Andre, 7, and four-year-old Louis-Philippe - are scheduled to be performed on Monday and Tuesday in Montreal.

An autopsy will also be performed on Laliberte, who likely took his own life, Gagne said.

Police investigators said no physical marks were found on the children's bodies and a spokesman said it's possible they were either poisoned or suffocated.

"We can confirm that the bodies of the children did not seem to have any marks of violence," provincial police Sgt. Gregory Gomez del Prado said earlier Saturday.

"But at this stage of the investigation we cannot confirm or deny anything (about how they died)."

The family had lived in the Abitibi region in northwestern Quebec before relocating to Saguenay around August.

As a result, most shocked neighbours in the quiet, well-to-do residential neighbourhood knew little about the family.

Police spent most of Friday inside the home gathering evidence; investigators were fanned out across the neighbourhood Saturday, talking to local residents.

Quebec provincial police were assisting the Saguenay police in their investigation.

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