The ED is tracking the whereabouts of these four persons, identified as Rabeya Bibi Mollah, Pratap Biswas and George Kutty. All of them are currently absconding and ED officials have reportedly activated all their sources to track them.

Sources said a close examination of various documents has revealed several transactions by Shahjahan and his family members with these four persons.

Sources said ED officials are reportedly taking the help of other central agencies to trace his whereabouts.

Authorities believe that once these four persons are in their custody, their interrogation will result in more important clues that will help them strengthen the case against Shahjahan.Sources said ED officials are also desperate to track down Shahjahan's younger brother Sheikh Sirajuddin, who is also absconding.

Sirajuddin was reportedly primarily responsible for handling the financial matters related to his elder brother's fish export business, which was a major means of diverting illicit income from various illegal sources.

Sources said another point which ED officials are trying to establish is how a part of the money in the crores of rupees ration distribution case was diverted through investments in Shahjahan Fisheries and fish export business. .

Sources said the account books of 50 persons, including Shahjahan, are currently under the scanner of the central agency, against whom investigating officers have obtained clues of receiving the proceeds of the ration-distribution case. In the coming time, ED officials will send notices to some of them for questioning.ED has already sent two summons to popular Bengali film actress Rituparna Sengupta for questioning in the ration-distribution case. However, she has still not appeared at the ED office.

Sheikh Shahjahan was arrested in February and has been in jail since then. After his arrest, he was suspended by Trinamool Congress.