Kolkata: An explosion rocked Dumdum's Motilal Colony on the Independence Day morning. According to sources, the blast took place in a house at 2 Motilal Colony on Saturday morning. The police have said that a person has been killed and two others injured in the blast. The police have already taken four in custody and have cordoned off the area. The locals have said that the blast might have taken place at the time of preparing the explosives. The officers have launched an investigation to see that if there was any other connection or trace to the explosion. 6 crude bombs and a large number of explosives have been recovered from the location, said the police sourcs.