New Delhi, April 12 -- Two senior National Investigation Agency (NIA) officers, Jaya Roy and Ashish Batra, who led the extradition process of Tahawwur Hussain Rana from the United States, are also leading a 12-member team to probe the charges against the mastermind of the 2008 Mumbai terror attacks.

The investigation agency was granted 18-day custody the day Tahawwur Rana was brought back to India. The NIA then began an extensive interrogation of the Mumbai terror attack mastermind to uncover the "deeper layers of the conspiracy" as the probe agency told a Delhi court it suspects he had plans to target other Indian cities as well with similar large-scale strikes.

The NIA's interrogation is focused on getting more details on his possible...