The boy was left unattended on the bus for more than half a day in central China's Hubei Province and found in coma in the afternoon, authorities said today.
He was sent to a hospital where he later died.
Police have detained two suspects, surnamed Wang and Hu, for negligence of duty and causing the death of the boy.
Wang was the bus driver for a Kindergarten in Shizi Township, while Hu was in charge of taking care of all the infants on the bus.
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The driver Wang then parked the bus at a nearby Internet cafe, took his breakfast and went home.
Wang found the boy on the bus in the afternoon when he was getting ready to pick up the children at the kindergarten, state-run Xinhua news agency reported.
Police are still investigating the case.