New Delhi, Nov. 28 -- The National Investigation Agency (NIA) has stepped up its investigation into the deadly suicide car bomb attack near Delhi's Red Fort, taking one of the arrested accused, Doctor Shaheen Saeed of Uttar Pradesh' Lucknow to Haryana's Faridabad for on-site questioning, sources said on Friday.

Shaheen is among seven arrested suspects arrested in connection with the November 10 blast that claimed 15 lives and left several others injured.

The agency believes that Shaheen, along with other arrested individuals played a crucial role in planning and executing the terror strike, which has prompted one of the most extensive counter-terror operations in recent months.

On November 20, the agency arrested Shaheen along with Dr ...