Quebec provincial police Sgt. Christine Coulombe said the mother is an important witness in their investigation into deaths the children, whose bodies were found Sunday in their home, the Canadian Broadcasting Corp. reported.
Police said they recovered the bodies of a 4-year-old boy and his two sisters, ages 5 and 2.
The name of the mother, 33, was not released.
Coulombe said the mother was taken to a hospital Sunday for reasons police hadn't determined.