The Andhra Pradesh police may consider seeking the United States' Federal Bureau of Investigation's help to analyse and harvest images of suspected bombers from a closed circuit television camera near the twin blast site here, sources said in Hyderabad on Monday.
The footage obtained from the camera near the twin bomb blast site have not yielded any credible clues so far, as images of three persons lurking near a bicycle, believed to be strapped with explosives, is not clear enough, sources said.
Sixteen people were killed and 117 injured in the twin bomb blast at Dilshuknagar in Hyderabad on Thursday.
"The footage was sent to a film laboratory in the city. However, there has been no headway. The quality of the picture could not be improved. So, the footage may be sent to FBI which has advanced technology," an official said.
The police have begun collecting call data transmitted before the twin blasts through cell phone towers located in the vicinity of the Dilshuknagar.
Investigators are also of the view that the twin blasts were not triggered by a remote control but by a timer device, sources said.
"It is difficult to use remote control for triggering the second blast as the first explosion would disturb waves and frequency. It would have made the second explosion difficult. So, the bombs might have been triggered by a timer," they said.
Intensifying the probe, the police collected guest registers of some hotels and lodges around the blast area and are verifying credentials of the occupants.
The police are yet to achieve a breakthrough even as 15 teams comprising officials from Hyderabad and Cyberabad police are investigating the blasts, besides the National Investigation Agency.