The CBI probing the case has decided to question some IB officers to understand the basis of the warning and the source of inputs, the agency sources said.
CBI sources said a Special Investigation Team constituted by Gujarat High Court had recommended probe into the role of the Intelligence Bureau officials.
They said CBI also in its probe has found some indications which require the role of IB officials to be probed.
They said CBI has also analysed intelligence input generated from the IB here cautioning the state police about Lashkar-e-Taiba's plan to attack BJP leaders L K Advani, Narendra Modi and VHP leader Praveen Togadia.
The sources who refused to give the names of the IB officers said the people who were handling VIP security wing of the snooping agency will be examined to understand the basis of the alert issued in 2004.
The agency will also investigate the inputs received by Gujarat Police that led to identification of a blue car, in which Ishrat Jahan was traveling, as the car in which the alleged terrorists were traveling, they said.
The CBI on the instruction of Gujarat High Court took over the probe of the alleged fake encounter in which 19-year-old Ishrat, Javed Sheikh alias Pranesh Pillai, Amjad Ali Rana and Zeeshan Johar were killed in Ahmedabad on June 15, 2004 by Crime Branch team led by DIG D G Vanzara.
A judicial inquiry report by metropolitan magistrate S P Tamang had alleged that 21 police officers, including then crime branch chief JCP P P Pande, suspended DIG D G Vanzara, the then ACP G L Singhal and ACP N K Amin were involved in the conspiracy regarding the encounter.
Vanzara and Amin are also accused in the fake encounter killing of alleged gangster Sohrabuddin Sheikh and in the murder of his wife Kausar Bi and are at present in jail.
The High Court had ordered the CBI to also probe the claims made by the state police after the encounter that Ishrat and the other three persons were LeT terrorists on a mission to kill Gujarat Chief Minister Narendra Modi.
The directives came as the Special Investigative Team constituted by the High Court had concluded that the encounter was staged by police.
The agency had filed the FIR after the Special Investigation Team probing the case gave its complaint to the CBI on December 15, 2011 charging all 20 policemen with murder and destruction of evidence.