The reports confirm that all three youngsters died violent deaths last Dec. 2.
The children's mother, Sonia Blanchette, is charged with three counts of first-degree murder.
The coroner says the two youngest victims, Anais, 2, and Loic, 4, were likely drowned. Both showed signs of bruises on the tips of their nose.
The eldest daughter, Lorelie, 5, likely died of a combination of drowning and asphyxiation caused by strangulation.
Toxicology reports reveal none of the children had drugs in their system.
Blanchette is slated to return to court on June 21.
She has been deemed fit to stand trial after having undergone a psychiatric evaluation.
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