The incident took place at a marriage venue on Murthal Road during marriage celebrations last evening, they said.
The injured are receiving treatment at the civil hospital here.
The police have lodged a case against three persons, including the marriage venue's owner, Sadar Police Station in-charge Bijendra said.
The venue's owner, Pramod Kumar, said it was clearly stated in the agreement that those booking the marriage palace will not be allowed to bring in arms and ammunition or any kind explosive items, including firecrackers.
According to the post-mortem report, the boy died due to injuries to his chest, police said.
The body has been handed over to his family members today, they said.
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