Kolkata, May 16 : At least three persons have been killed and four others severely injured in an explosion at a fire-cracker factory at Egra in West Bengal's East Midnapore district on Tuesday. The impact of the explosion was so tremendous that entire house in which fire-cracker factory was running collapsed completely. The policemen suspect that more bodies will be recovered after the rescue operation is completed. The four injured persons have been shifted to a nearby hospital, where their condition is said to be critical. The police are investigating whether the explosion was just because of the fire-crackers stocked there or because of the explosion of crude bombs that might have been manufactured there under the garb of the fire-crackers factory. The local people have alleged that the said fire-cracker factory was running in a totally illegal manner without requisite permission or monitoring of the local administration including police. The local people have also alleged that their repeated appeals for taking action against the illegal fire- crackers factory mushrooming in the area were ignored by the local administration. Till the time the report was filed, a huge police contingent had arrived at the spot. The policemen have cordoned off the entire area. To recall, in the closing part of the previous year, a similar explosion occurred in Bhupatinagar, also in East Midnapore district. There persons, including a local Trinamool Congress, leader were killed and several others injured in that explosion. /IANS