The boy identified as Sonu was playing outside his house located in Sant Nagar in Rani Bagh before he went missing.
His father, Ramgopal, lodged a report with police in the morning.
“But around 4 p.m., his neighbour Vijay Ahuja found Sonu dead on the rear seat of his car,” a senior police officer said, adding that the car was parked outside the deceased’s residence.
Prima facie, Ahuja was cleaning his car around 11 a.m when Sonu sneaked inside. But he was trapped as the car was fitted with a central locking system which the boy could not unlock.
According to the police, Sonu was trapped inside the covered car and suffocated to death.
“However, we are waiting for the post mortem report to ascertain the actual reason of his death,” he added.
Meanwhile, the police is also questioning Ahuja.