Surendra Kumar Jha, the child's father, Wednesday alleged that doctors had left inside his lungs the locket the kid was wearing on his neck.
"I don't know how they did it but x-ray reports have confirmed the case," Jha told reporters.
M.S. Chopra, chief medical officer of the hospital, said they were investigating the matter and the allegations can only be confirmed or denied Thursday.
The incident came close on the heels of two cases of medical negligence at the premier All India Institute of Medical Sciences (AIIMS) here.
In one case a 12-year-old boy was killed after his heart surgery and in the other case a 75-year-old man died after a senior cardiologist left a metal screw inside the heart during an operation.