A 4-month old baby was killed and two other children seriously injured in an accident last night in Donnaconna, Que.

Police say the baby's mother lost control of her car after a passing manoeuver and plunged into a ditch. The baby was thrown from the vehicle.

The driver and a female passenger -- the mother of the other two children -- were treated for slight injuries and nervous shock. The victims have not been identified, although the driver and her child are said to be from the Trois-Rivières area.

Authorities are investigating the accident and will inspect the car seat the child was riding in