Investigations into the serial low-intensity blasts in Pune are making slow progress as CCTV cameras at the explosion sites have been found to be non-functional.
The CCTV cameras installed at Dena Bank, McDonald's and Bal Gandharva traffic square, in the vicinity of which the explosions occurred, have not yielded any clue so far and some of cameras were non-functional, sources from the investigative agencies cited by Hindustan Times said on condition of anonymity.
According to the sources, the Maharashtra ATS, city crime branch and the NIA were looking for clues from the bicycles at the site, as two of the four coordinated explosions happened in their front carriers.
Explosives strapped to the bicycles appear newly purchased and investigators are trying to locate the shop from where these were purchased in order to nail the perpetrators.
According to reports, a black sticky substance with ammonium nitrate was used in the explosions, and forensic experts were also trying to ascertain the concentration of explosives in the devices to zero in on the likely groups behind the blasts.
Sources say different terror groups use varying concenrations of explosives in their "signature bombs". Some reports say battery operated detonators with digital timers could have been used for triggering the blasts.