One Ismail Fakir or Boral was making crude bombs in his house and three of his neighbours had gathered in the room to witness the process, when the bomb went off, said a senior police officer.
Though Ismail escaped unhurt and managed to flee the spot, Israfil Fair, Saraf Mistry and another person were injured in the blast and were admitted to a local hospital, he said.
A search was on to trace the whereabouts of Ismail and investigations were on, the officer added.