Calcutta, Jan. 22 :    Calcutta, Jan. 22:  Security agencies launched a massive manhunt in several areas of central, south and east Calcutta and seized a large number of incriminating documents. Police, CID and IB officers simultaneously combed the dingy Mafizul Islam Lane, Darga Road, Ripon Lane, G.G. Khan Road, and Topsia First and Second Lanes, where they came upon the papers. According to sources close to officers who took part in the raid, 20 suspects in their twenties and thirties have been detained for interrogation. Deputy commissioner of police, eastern suburban division, Sanjoy Mukherjee, said: 'Enquiries are on in a few areas but we cannot share the details for security reasons.'' According to police, the documents contained details about the suspects' contacts in Mumbai, Delhi and Lucknow. 'We have got some contacts and telephone numbers in Karachi, Lahore, Dubai and Sharjah,'' the police officer said. Sources said sleuths have found the bank accounts of 'social service organisations' (which camouflage their dark activities) with substantial bank balance. According to information available with the IB and CID, which investigated Khadim's vice-chairman Parthapratim Roy Burman's kidnap case, Asif Reza Khan, alias Rajan, and his brother, Amir Reza Khan, were militants and members of Harkat-ul-Jihad-e-Islami. The city and its adjacent areas went on high alert after the killings. State director-general D.C. Vajpai said policemen were told to frisk passengers at Howrah and Sealdah stations and also at Calcutta airport. 'We have sealed the entry and exit points. All outgoing and incoming vehicles are being checked,' Vajpai added. Police beefed up the security measures in front of American Center. Policemen with Sten guns have been deployed. A sandbag bunker has been put up in front of the main gate. 'We are also beefing up the security arrangements in front of other foreign embassies. But we cannot ensure their safety. I can tell this much - we will try our best to resist such attack within our limited capacity,' said commissioner of police Sujoy Chakraborty. Police launched a manhunt immediately after the incident. Special branch and detective department officers raided different areas in the city and picked up 50 people. 'We are interrogating them. We are trying to find out where they were and what they were doing during the incident,' said Chakraborty. Police made drastic changes in the security arrangement for the Republic Day parade. 'Usually, a few armed policemen are deployed in front of the guests' gallery. This time, we have decided to strengthen the security ring as much as possible,' Chakraborty said. At a high-level meeting with the chief minister, the detective department has been asked to investigate the shoot-out. Six teams have been formed under the supervision of DC-I, DD Soumen Mitra. 'Altogether 50 officers have been involved in this case. We have not got any lead so far. The motorbike still remains untraced,' said Mitra.