WASHINGTON - Investigators from India have extensively interviewed David Headley, the former Philadelphian linked to the 2008 Mumbai attacks, the Justice Department announced Thursday.

The department said Headley, in detention in Chicago, answered the Indians' questions over seven days.

He pleaded guilty to a U.S. court in March to helping plan the November 2008 attacks in Mumbai, as well as subsequently aiding a plan to attack a Danish newspaper over cartoons depicting the Prophet Muhammad. That plan was not carried out.

India blames Pakistani extremists for the Mumbai attacks, which left 166 people dead, including six Americans.

In his plea deal, Headley, 49, admitted making surveillance videos and conducting other intelligence-gathering for the attack on Mumbai.

The United States and India say the 10 gunmen in the three-day siege were trained and directed by the Pakistan-based group Lashkar-e-Taiba (Army of the Pure).

Headley and his counsel agreed to the meetings, and there were no limits on the questions posed by the Indian government, the department said.

Headley's mother was the late Philadelphia socialite and tavern owner Serrill Headley. His father, Syed Saleem Gilani, who worked at the Pakistani Embassy in Washington, also has died.

Indian law enforcement officials were provided access to Headley "as part of the cooperation and partnership between the United States and India in the fight against international terrorism," the department said in a statement.

Both countries have agreed not to disclose the substance of the interviews so as to protect the confidentiality of the investigations, the Justice Department statement added.

A report in the Times of India on Thursday alleged that Headley had linked Pakistan's ISI intelligence service and several Pakistani army officers also to the Mumbai attacks. The paper did not cite its sources, and Pakistan has denied any official links to the attackers.

Last week, U.S. and Indian officials wrapped up high-level strategic talks aimed at easing Indians' fears that their country was slipping behind rivals China and Pakistan in U.S. foreign-policy priorities.

India is seen as crucial to the U.S.-led fight against extremists in Pakistan and Afghanistan, as a counterweight to China, and as a big part of settling trade and climate-change deals. President Obama is to visit India in November.

The Bush administration in 2008 pushed through a landmark accord to establish civilian nuclear trade with India, transforming ties after decades of mistrust.

As part of Headley's plea-bargain agreement, the U.S. government agreed not to extradite him to India, Pakistan, or Denmark for the charges to which he admitted guilt.