Calcutta, March 28 :     A crackdown on a ration card racket, which could run into crores, has prompted the government to launch a drive to withdraw all 'old' ration cards and replace them with new ones with photo-identity kits attached. Three people carrying a sheaf of what appeared to be fake ration cards were detained by the police on Tuesday from near a ration shop in south Calcutta. Officials said the impounded cards were sent to senior food department officers for verification. State food minister Kalimuddin Shams said his department had started the process of withdrawing old ration cards from the market and replacing them with new ones. 'We know that fake cards are in circulation and so we have decided to speed up the process of new photo-ration cards. We hope to complete the process of replacing the cards by the end of this year,'' he added. According to Shams, the new cards will be available from local ration shops. 'A card-holder will have to deposit the old one, which will be sent to the zonal office for verification. The card-holder will also have to submit a passport-size photograph to the local ration shop,'' explained the minister. Senior food department officials were involved in a series of meetings through the day. Sources said food secretary Dipak Rudra urged the officials to speed up the process of withdrawing old cards and replacing them with the newer, sleeker, photo-cards. Police said ration cards are being sold for Rs 2,000 a piece in different areas. Investigations show there are 50,000 fake cards in circulation. Officers of the enforcement branch swung into action on Tuesday morning after being tipped off about forged ration cards, bearing the seal and signature of authorised persons, being sold from zonal and divisional ration offices. 'It is very difficult to distinguish between the original and fake ration cards. The racketeers are experts at the job and run a well-oiled operation,'' explained deputy commissioner of police Ranjit Pachnanda. 'The racketeers have already raked in about a crore of rupees by selling these fake cards,'' said a police officer.