Police are investigating the deaths of three young children in Drummondville.

The lifeless bodies of two girls, Anais, 2 and Lorelie, 5, and their four-year-old brother, Loic, were discovered Sunday afternoon in a house on Turcotte St., apparently by their grandmother.

At this point police don't know who called 9-1-1 at 4 p.m Sunday afternoon, but neighbours said they heard a scream about the same time. Some neighbours believe it was the children's grandmother who discovered their bodies.

Those witnesses also saw police remove 33-year-old Sonia Blanchette, the children's mother, from the home. She has been taken to hospital for observation and has yet to speak to police about what happened.

"We don't fear for her life, however she is an important witness," said Surete du Quebec spokesperson Daniel Thibaudeau.

Neighbours also said that the children's father, Patrick Desautels, visited the house later in the day. The parents apparently separated about a year ago, and the children are believed to have been in the father's custody.

Blanchette was arrested and charged last year with breaking a custody order. The case is still before the courts.

In a press release issued Monday, Desautels said he will speak to reporters Tuesday afternoon, and asked the media in the meantime to allow the family to mourn privately.

"We are currently with family. This tragedy leaves us speechless. The police investigation will tell us more about the circumstances of the tragedy. What occurred is inexplicable," said Desautels in the news release. Desautels also added that he deeply loved his three children and that he will miss them the rest of his life.

A friend of Blanchette's, who asked to remain anonymous, said the mother was having a difficult time lately.

The coroner's office said it will not comment on the matter until autopsy results on all three children are complete.

Police say there are still unanswered questions.

"Were the children here on a legal supervised visit? What was the custody arrangement?" said Thibaudeau.

It is believed the grandmother had some role in the supervised visits.

Family lawyer Maria Battaglia said those kinds of custody arrangements are exceptional.

"It sounds to me like this case may have fallen through the cracks or could be that this person's particular circumstances were more serious than was believed. But of course, when we sit here and look at it in hindsight, it is very easy to say that something went terribly wrong," she said.