Indian investigators have spent seven days quizzing an American who pleaded guilty to helping a Pakistani extremist group, Lashkar-e-Taiba, plan the November 2008 terrorist attack in Mumbai.

The State Department said that the Indians were given access to David Coleman Headley "as part of the cooperation and partnership between the United States and India in the fight against international terrorism."

"Mr. Headley and his counsel agreed to the meetings," said a State Department press release. "There were no restrictions on the questions posed by the Indian investigators."

So what did Headley tell his interlocutors from India's National Investigating Agency? The State Department wasn't saying.

"To protect the confidentiality of the investigations being conducted by both India and the United States, both countries agreed not to disclose the contents of the interviews," the State Department said.

Indian news reports, however, said that Headley implicated Pakistan's chief intelligence agency, the Inter-Services Intelligence Directorate, in the attack, an allegation denied by Pakistan.

Headley pleaded guilty on March 18 in U.S. court in Illinois to 12 federal terrorism charges. He admitted scouting locations and providing advanced support for the Mumbai attack that left 163 people dead and more than 300 injured, as well as to plotting to attacking a Danish newspaper that published cartoons in 2005 of the Prophet Mohammad.