Sarnia police said an examination of the vehicle found nothing mechanically wrong. It sank in the St. Clair River on Dec. 3 with two small children inside. (Sarnia Police Service)

A woman from Wallaceburg, Ont., near Sarnia, is facing multiple murder charges after the car she was driving went into the St. Clair River, killing two of her grandchildren.

Jane LaMarsh, 48, is charged with two counts of first-degree murder and one count of attempted murder.

On Dec. 3 at 7:10 p.m., LaMarsh was driving on St. Clair Parkway with three children in the car, her daughter, Jennifer LaMarsh, 12, her grandson Tyler Bernard, 10, and granddaughter Taiya Talbot, 6.

Taiya Talbot, 6, and her brother Tyler Bernard, 10, were supposed to be going Christmas shopping with their grandmother, Jane LaMarsh, when the car they were in sank in the river. (Facebook)

Police said LaMarsh told her daughter, Stephanie Bernard, that she was taking all three children Christmas shopping.

It is alleged that she drove along the shoreline road, known locally as River Road, but stopped near the Suncor refinery where she made a U-turn and drove the car into the river.

As the car began to sink, police said LaMarsh and her 12-year-old daughter managed to escape the vehicle. Taiya and Tyler did not. Police divers tried for 90 minutes to pull the children from the sunken vehicle, and when they did were unable to revive them, said police Sgt. Scott MacLean.

'There was no mechanical or environmental or any reason why the vehicle would have left the roadway and veered into the water.'—Sgt. Scott MacLean

"Tyler was in the front passenger side, and Taiya was in the middle rear," said MacLean.

"Jennifer was able to get out the back because of her persistence. It was extremely difficult, in her words, and I can imagine because of the way the car landed in the water and the current that was pushing on the passenger side."

Taiya and Tyler are shown in a photo from Facebook.

Sarnia police officers arrested LaMarsh at her home in Wallaceburg on Thursday.

They said their investigation turned to LaMarsh after an inspection of the car she had been driving the night the children died determined there was nothing mechanically wrong with the vehicle.

During the arrest, officers seized computers from LaMarsh's home.

At a press conference Friday, Sarnia police would not say whether the children's mother had spoken to LaMarsh since the incident, because they said family dynamics play a role in the investigation.

When asked by reporters if the deaths were part of a murder-suicide attempt, MacLean said, "That's something that's part of the evidence … yet to be determined, but as I say there was no mechanical or environmental or any reason why the vehicle would have left the roadway and veered into the water."

Police confirmed that the cause of death for the two children was drowning.

LaMarsh made a brief court appearance in a Sarnia courtroom Friday, and is due back in court on Feb. 26.

With files from Heather Wright