Sources in the NIA team, which questioned Headley in Chicago in June, told Rediff.com that their interrogation focused on the involvement of ISI officers in the Mumbai terror attacks.
NIA sources said Headley revealed that three ISI officers -- Major Haroon, Major Sameer Ali and Major Iqbal -- were associated with the 26/11 terror plot.
According to NIA sources, Headley spoke at length about the ISI's role in the terror siege of November 2008.
The Pakistan-American was assigned the identification of likely terror targets in Mumbai and consistently reported to these ISI officers.
Headley told the NIA team that the ISI and Laskhar jointly planned the attacks.
Even as the Lashkar terrorists terrorised Mumbai, an ISI officer monitored the situation on the phone, Headley claimed, adding that one of the officers also spoke to the terrorists.
The ISI officers also coordinated with Headley while the latter scouted targets in Mumbai. Headley, who was arrested by America's Federal Bureau of Investigation last October as he was about to fly out of Chicago, communicated with these ISI officers on e-mail. He handed them his survey of the likely targets.
Headley's revelations match statements Al Qaeda operative Ilyas Kashmiri made recently to a Pakistani Web site. Kashmiri planned the terror siege, originally called the Bombay Project.
But the ISI involved the Lashkar as it felt the organisation was better equipped to strike in India.
All those involved, barring Lashkar founder Mohammad Saeed and the three ISI officers, worked on the operation on a need-to-know basis, Headley told the NIA team.
He revealed that Saeed scrutinised each and every detail of the Bombay Project.
Lashkar terrorists involved in the conspiracy sought Saeed's permission if they needed leave, Headley disclosed.
He added that when his wife complained to Saeed that her husband never had any time for her, she was told that the Bombay Project would suffer if Headley was granted time off from his deadly mission.