'Headley and his counsel agreed to the meetings (with the Indian investigators) and Headley answered the Indian investigators' questions over the course of seven days of interviews. There were no restrictions on the questions posed by Indian investigators,' said a statement from the US Justice Department.
A four-member team of NIA officials, led by Loknath Bahera, questioned Headley face-to-face, eliciting information about his role in the Mumbai attacks, the wider conspiracy and all those involved in the carnage.
'As part of the cooperation and partnership between the US and India in the fight against international terrorism, Indian law enforcement officials were provided direct access to interview David Coleman Headley,' the statement said.
To protect the confidentiality of the investigations being conducted by both India and the United States, both countries have agreed not to disclose the contents of the interviews, the statement said.
Headley had, on March 18, pleaded guilty to conspiring in the 26/11 Mumbai attacks in November 2008, as well as later planning to attack a Danish newspaper, but struck a deal with US authorities in a plea bargain that saved him from the death penalty and extradition to India.
The plea agreement, however, had said Headley would cooperate with foreign authorities and can be interviewed by them only on US soil.
India had asked the US to grant access to the 49-year-old Headley, being held in the federal lock-up Metropolitan Correctional Centre in Chicago.
NIA concludes questioning Headley
Coverage: The case against David Coleman Headley