Officers are now investigating whether she cooked the child alive or if she killed the girl then tried to burn her remains, HLN reports.
When police arrived on the scene she allegedly told them: "We both had to burn. That was the only way we could go to heaven together."
The paper spoke to neighbours who said the woman had been depressed for some time after going through a divorce.
She had been living with her mother at the time, but the older woman was reported to have left the house on the evening in question.
Due to the mother's physical and mental state, she was not immediately interviewed by investigators.
An autopsy on the young girl has already been performed, although the prosecutor's office of Halle-Vilvoorde have not yet made the results public.
According to psychiatrist Hans Hellebuyck, it is "hard to estimate" what exactly goes through peoples' minds in cases like this.
He said that if the mother did indeed say that she started the fire because only the soul of cremated bodies enter heaven, could be a sign of psychiatric problems.
Hellebuyck said: "If the woman made such remarks and truly meant them, it is possible that she is mentally ill. I am not saying it is like that, but it is something which has to be taken into account."
WHERE TO GET HELP:
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
OR IF YOU NEED TO TALK TO SOMEONE ELSE:
• LIFELINE: 0800 543 354 (available 24/7)
• SUICIDE CRISIS HELPLINE: 0508 828 865 (0508 TAUTOKO) (available 24/7)
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