CLOQUET, MN (KDAL) - A 3 year old boy was left behind in a Fond du Lac "Head Start" bus Monday morning until a passerby heard his cries three hours later. The school bus driver is on administrative leave while an investigation into the incident is underway. The Fond du Lac Band says its unclear why the driver didn't check to make sure all the students had left the bus. It is believed that the child fell asleep in his seat. Temperatures were around the zero mark at the time and the boy was taken to a hospital for observation and then released.