The incident took place when the boy, who was reportedly a rag picker, was lifting solid waste behind a wall at Gandhipath in Vaishali Nagar area which was razed by a bulldozer of JDA during the drive, they said.
Scores of JDA workers immediately clered the debris to rescue him, police said, adding, he was rushed to SMS hospital.
JDA is on a drive since the last couple of days against illegal encroachments, especially marriage gardens and other restaurants constructed in Vaishali Nagar area.