A 7-year-old boy died early Sunday after the car he was riding in was rear-ended by a truck on the Meishin Expressway in Takatsuki, Osaka Prefecture, police said.
The boy, Yoshitaro Nishimae, of Nishinomiya, Hyogo Prefecture, was on his way home from the World Expo in Aichi Prefecture, investigators said.
Police said the truck, driven by Kei Kawase, 34, rammed into the car, pushing it into an adjacent lane. The car was struck by another sedan and ended up on its side.
Police arrested Kawase at the scene on suspicion of professional negligence resulting in injury, but were to question him on suspicion of negligence resulting in death.