The recovery of live bombs after the blast at the Mecca mosque in Hyderabad has revealed the use of a cellular phone to complete the circuit in the explosive. This has led the investigators to take a close look at the explosion at the Special Task Force (STF) headquarters in Hyderabad in October 2005 in which a similar circuit was used. The circuit is completed once the mobile phone starts ringing.

The STF headquarters blast was traced to the Bangladesh-based Harkat-ul-Jehad-e-Islami (HUJI) after the Delhi police caught three militants from the group in December 2005. They reportedly admitted to ferrying the three people responsible for the blasts. The similarities in the circuit of the explosive device in both the blasts have brought HUJI under the scanner again. The focus now is on HUJI’s Shahid Bilal whose group was apparently behind the STF blast.

The police, sources said, would begin by questioning those involved in the planning and execution of the blasts at the STF headquarters. In that investigation, it had come to light that one of the arrested had undergone training in ISI-run camps.

Friday’s blast bears the stamp of a recent trend to target mosques with IEDs made mostly from locally available material with an aim to stoke communal passions. The new modus operandi of the terrorists involves elements from outside India and local recruits who are trained to make low-intensity explosives.

The blasts at Delhi’s Jama Masjid, Malegaon and on the Samjhauta Express are some of the recent ones in which investigations have yet to yield any convincing result. The fear is that the Mecca mosque blast will also join this list of unsolved cases.