Headley has been accused of planning an attack on a Danish newspaper after it ran cartoons of Prophet Muhammad, and of his involvement in the 26/11 Mumbai attacks.
The FBI team, during its current visit to New Delhi, is said to have shared material it collected with Indian investigators about Headley's involvement in the November 2008 attacks.
Headley, 49, has been charged in a 12-count criminal information with six counts of conspiracy to bomb public places in India, to murder and maim persons in India and Denmark, to provide material support to foreign terrorist plots, and to provide material support to Lashkar-e-Tayiba, and six counts of aiding and abetting the murder of American citizens in India.
According to the latest charges, Headley changed his name from Daood Gilani in February 2006, in Philadelphia, in order to present himself in India as an American who was neither Muslim nor Pakistani.
He later visited Mumbai five times, in September 2006, February and September 2007, and April and July 2008, and each time took pictures and made videos of various targets, including those attacked on 26 November, 2008.
After each trip that Headley took to India between September 2006 and July 2008, he allegedly returned to Pakistan, met with other co-conspirators and provided them with photographs, videos and oral descriptions of various locations.