The agency, in the meanwhile, has started scrutinising the documents recovered from searches at the five offices of Hindalco and residence of Parakh in Hyderabad on October 15.
The sources said the agency would question Birla and Parakh in connection with the case but that might take time as CBI officials would first examine the documents to gather material evidence.
Sources said the FIR is the first step and all the allegations would be probed during the course of investigations.
They said the agency has named people in the FIR only on the prima facie evidence basis and further investigation is going on.
