Power supply in Basheer Nagar area has been disrupted following the explosion at the fabrication workshop , Commissioner of Police Sanjay Kumar said.
A blast in a gas cylinder was suspected to be the cause of the mishap, but police said it was yet to be confirmed.
The walls of the workshop were severely damaged because of the blast and the place was sealed owing to fear that its walls may collapse, Kumar said.
The deceased have been identified as - Shaikh Rafiq Ahmed (30), Khan Majeed Hayat (52), Shaikh Muzaffar Ahmed (22) and Shahzad Siraj Khan (3).
The deceased belonged to Bihar and were employees at the workshop.
Police said two persons, including the owner of the workshop, died on the spot while two others succumbed during treatment at a hospital.