Investigations into the July 13 triple blasts have thrown up similarities with the German Bakery blast in Pune in 2010 and the unsuccessful attempt at serial blasts in Surat in 2008.
Forensic experts told Hindustan Times that explosives used in Mumbai had much in common with the ones used in the German Bakery blast in Pune and the unexploded bombs in Surat. "The circuit is similar to the one used in the German Bakery blast," said a forensic expert on condition of anonymity. “The only difference is that TNT was used in Mumbai, while RDX was used in Pune.”
The source added that a mobile phone alarm was used to trigger the detonator in the July 13 explosions. Digital timers with intergrated circuits were used as triggers in 2008 in Surat — a technique used for the first time outside of the Jammu & Kashmir. The chargesheet filed by the Anti-Terrorism Squad (ATS) in December 2010 also points to the use of a mobile phone alarm as a trigger in the Pune blast. (Forensic experts, though, have not found any evidence to support the ATS’ claim).
Mohammed Arif Badruddin Sheikh alias Arif Badar alias Laddan (38), an Indian Mujahideen (IM) operative, told Mumbai Crime Branch after his arrest in September 2008 that the 29 bombs planted in Surat did not explode because of a faulty circuit. “A minor error in power supply of transistors failed to trigger the bombs. But with Mumbai blasts, the terrorists seem to have rectified the error,” added the forensic expert.
Sources reveal that the technique of using digital timers to trigger explosives has been perfected by the Al Qaida-linked Indonesian terror group Jemaah Islamiyah (JI).
Members of banned outfits Harkat-ul-Jihad-al Islami Bangladesh (HuJI-B) and the Lashkar-e-Taiba arrested in Uttar Pradesh and Delhi, respectively, have told interrogators about the presence of Indonesian nationals in terrorist camps where a few Indians were trained.
Police sources said that the arrested operatives would be questioned to establish the identity of Indians who had undergone terror training at these camps.