The prime focus of the investigation is on former West Bengal education minister and Trinamool Congress Secretary General Partha Chatterjee and his close aide Arpita Mukherjee.

The Benami Transactions (Prohibition Act) disallows financial transactions in which property is transferred to one person for consideration paid by another.

Sources said that the I-T Department wants to initiate this new line of investigation by questioning Arpita Mukherjee, who is currently behind bars at a correctional home in South Kolkata.

Sources added that the I-T Department has submitted an application at a special court of the Prevention of Money Laundering Act (PMLA) in Kolkata, seeking permission to question her.

Depending on developments, the I-T Department officials will make a similar plea to question Partha Chatterjee, who is also behind bars in the case.

The new move was initiated after the ED and CBI officials probing the case identified several properties in the names of other people but which were paid for by the former minister and his close aide.

Sources said the case is being probed by three central agencies from different angles.

While the CBI is looking into the criminal angle, the ED is taking the money laundering line and the I-T Department is probing benami transactions.