Injured shop owner K G Agarwal, his son Rajesh, a servant Mahveer, and a passerby Firoz were rushed to Mahatma Gandhi Hospital, SHO Bheemganj Arjun Singh said.
The incident occurred when the trio were opening the shop around 1000 hrs and the leaked LPG-gas cylinder caught fire leading to blast, SHO said.
A case has been registered against the shop owner for running an unauthorised repair and selling of gas stoves, he added.