A suo motu case has been registered against unknown persons in connection with Tuesday’s explosion in North Kolkata’s Nager Bazaar amidst media reports that NIA has taken serious note of the mishap in which a minor boy was killed and nine others sustained injuries.Investgative offices are yet to identify the culprits saying the probe is at an early stage. BJP and other opposition parties allege that bomb making culture is being promoted by vested interests in the eastern state as India and neighbouring Bangladesh having border with West Bengal are approaching parliamentary elections later this year.Samples have been collected from the spot and forensic tests are being conducted to ascertain what type of material was used in the blast in Nagerbazar in North Kolkata.CCTV footage from neighbouring shops as well as those from the traffic police are being checked. Locals of the neighbourhood have also been asked to cooperate in the investigation .Inputs from locals could be vital and help in identifying those behind the blast, the police officer said. Asked if the explosion could have been fallout of internal squabbles in the ruling Trinamool Congress, as has been alleged by the BJP, the police officer said it is difficult to infer such things at this stage since no arrests have been made in the case so far. Nobody has been identified for the heinous act .It is very difficult to say whether the victim was affiliated with any political outfit since the investigation is at a very early stage, sources said. Earlier, Police described Tuesday’s blast as a low-intensity one that occurred outside a fruit shop on the ground floor of a building which houses the office of South Dum Dum Municipality Chairman and Trinamool Congress leader Panchu Roy.As the TMC is facing stiff contest in the coming Lok Sabha poll from the BJP, some ruling party’s leaders including a junior minister accused the BJP-RSS of planting the bomb in the crowded area drawing flack from the saffron outfits.RSS reportedly filling defamation suit against the accusers.