Quebec police are investigating after three children were found dead in a home northeast of Montreal Sunday afternoon.

Provincial police confirmed that the children, two girls aged 2 and 5, and a boy, 4, were found dead on the top floor of a red-brick duplex in Drummondville, which is about 100 kilometres northeast of Montreal. The children are believed to be siblings, and police told CTV News late Sunday a 33-year-old woman, believed to be the children’s mother, is an important witness in the investigation.

Neighbours described a chaotic scene outside the home. They said they heard screams and saw police officers taking the woman believed to be the children’s mother out of the house, said CTV’s Montreal Bureau Chief Genevieve Beauchemin. Neighbours also said they believed they saw the children’s father at the home earlier in the day, Beauchemin reported.

Police are still working to confirm those details.

Police have deemed the deaths suspicious.

Police received a call at 4 p.m. Sunday, Sgt. Christine Coulombe told in a telephone interview. Ambulances were outside the home earlier, but had departed by late evening.

Drummondville Express photojournalist Ghyslain Bergeron told CTV News Channel that police set up a large security perimeter around the house as the investigation got underway.