16 persons were killed and 117 injured when two explosions, separated by minutes, rocked Dilsukh Nagar area in the city last Thursday.
The footage, captured by a CCTV camera installed in vicinity of the blasts site, of three persons lurking nearby a bicycle, believed to be strapped with explosives, is not clear enough, sources said today.
Stepping up their investigations, the police have started collecting the call data transmitted through mobile phone towers located in the vicinity of Dilshuknagar prior to the explosions.
According to sources, investigators are of the view that the blasts were not triggered by remote control but a timer device.
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"It is difficult to use remote control for triggering the second blast as the first explosion would have disturbed waves and frequency. It would have made the second explosion difficult. So the bombs might have been triggered by a timer", sources said.
Police are yet to achieve a breakthrough even as 15 teams comprising officials from Hyderabad and Cyberabad police are carrying out investigations into the blasts, besides the National Investigation Agency.