Counter-terrorism investigators probing the twin blasts in Hyderabad's busy Dilsukhnagar shopping area on Thursday have found "useful CCTV footage", while seeing an Indian Mujahideen (IM) imprint on the terror attack.
"The CCTV footage is being analysed to spot the people who planted the bombs," a senior investigator who did not want to named said on Friday.
"There is no conclusive evidence yet, but the use of nitrate-based explosives, shrapnel, bicycles to plant the bombs and the choice of the sites to inflict maximum casualty point to the IM."
Remnants of the bicycles have been sent for forensic examination, while a hunt is on for identifying their buyers and sellers. The IM had used bicycles to execute the May 2008 and August 2012 Pune blasts as well.
Investigators believe the improvised explosive devices had timers and up to one kg of explosives were used at both sites — outside a fast food joint and a bus shelter 100 metres apart. The use of the more lethal RDX (Research Department Explosive) in the blasts has been ruled out.
The blasts were executed around seven months after two alleged IM operatives surveyed the stretch on the directions of the terror outfit's co-chief Riyaz Bhatkal. "On the directions of Riyaz Bhatkal, IM operatives Sayed Maqbool and Imran Khan had done a reconnaissance of some spots in Dilsukhnagar along with two other spots in July 2012 on a motorbike. Due to some logistical reasons, the attack was not carried out then," said the investigator.
"We suspect Maqbool and Imran gave their feedback to Riyaz — hiding in Pakistan after the Batla House encounter in Delhi in 2008 — before the Delhi Police arrested them."
Another investigator said the twin blasts occurred at sites close to a spot where bomb experts had defused a bomb planted on a motorcycle by IM operatives on August 25, 2007. "The same day, two other bombs planted by IM operatives had exploded at fast food eatery Gokul Chat Bhandar and Lumbini amusement park. The August 2007 blasts in Hyderabad were directly supervised by Riyaz."
The investigator pointed out that much like Thursday's attack, the IM had targeted a bus shelter at Kabutarkhana near the Dadar suburban railway station when it executed the Mumbai July 2011 serial blasts.