The incident took place in the wee hours at Rajanagaram, when victims -- S Yesu (24), his wife�Mani (20) and son Munna (4) -- were fast asleep, they said.
However, four others who were sleeping in another room escaped unhurt.
An electric short circuit led to the explosion, Rajahmundry DSP (Urban) Satyanand said. �
The trio were burnt beyond recognition, police added.