According to Dawn, police said the speaker-shaped object had been brought home from a junkyard in Naik Town, near the family's residence.
The boy reportedly took the object into a room where his mother was sitting. Mistaking it for a toy, he began playing with it and attempted to dismantle it, triggering an explosion.
Both the boy and his mother sustained fatal injuries and died on the spot, police said.
Multan City Police Officer (CPO) Akhtar Farooq told Dawn that he had visited the scene and spoken to local residents.
He added that police were collecting evidence from the site to establish the circumstances surrounding the incident.