Government has already handed over the case to National Investigation Agency (NIA) within hours of the explosion, which was a repeat of May 25 when a low-intensity blast rocked the High Court.
New Delhi, Sep 7 blast is the first case of terror attack in Delhi to be transfered to NIA, which was set up after the 2009 Mumbai terror attack case.
Police is yet to crack the May 25 explosion outside the High Court though the Special Cell had questioned several people. Investigators had recovered some nail-like shrapnel, a battery-like object and ammonium nitrate from the spot, sources said adding nails and bolts were packed and detonator was attached to the timer.
Sources then said this pointed to the possible involvement of Indian Mujahideen as the crude bomb had the signature of the terror outfit's methods.
Hot on the heels of the May 25 blast, a torn polythene bag containing silver colour powder, pencil batteries and wires discovered outside a women's college on Sep 7 triggered a security scare here.
Besides the May 25 explosion, police is yet to crack the 2006 blast in Jama Masjid, the 2008 Mehrauli blast or the 2010 terror attack infront of Jama Masjid.