CLOQUET — The Fond du Lac Band of Lake Superior Chippewa is investigating why a 3-year-old boy was left on a bus for about three hours in freezing temperatures.

Brooklyn Wait said her son, Ty Stiffarm, was treated at a hospital in Cloquet after he was found on the Fond du Lac Head Start bus Monday.

The tribe said the driver of the bus did not check to see if all children had left the bus when they were dropped off at Head Start near Cloquet. Wait said that school staff should have taken attendance right away when the children arrived, then they would have known her son was missing.

Someone passing by the bus about 11 a.m. heard the boy screaming and called for help.