Police say they are looking for Jaden Khalifa, 3 and Caleb Brisebois, 1.
Police say the children were taken by Catherine Otim.
They are looking for a car they identify as a 2007 Toyota Yaris with Ontario licence plate BWHZ018.
Police say one of the boys was to be returned to his father Saturday evening but never was.
Police say comments were made indicating the children were in danger.