Sources said files related to appointments of senior officers in Railway Protection Force have been sought by CBI in this connection.
Under the CBI scanner is the posting of a Director General Of RPF who had reportedly superseded 25 officers to become the head of the force during Mamata Banerjee's tenure in May, 2011.
However, the agency sources said they are not targetting any individual in their probe and they would be looking into all aspects of appointments and promotions in the RPF while probing alleged corruption.
The bribery scandal involving former Railway Minister Pawan Kumar Bansal's nephew Vijay Singla and Railway Board member (staff) Maghesh Kumar has opened a can of worms and many complaints of alleged corruption in various departments are coming to CBI, they said.
The sources said agency would take action only after it finds some concrete material to initiate an inquiry into allegations of corruption.