Up to 100 detectives are involved in the hunt for the terrorist killers of Constable Ronan Kerr.
Working in four teams, the detectives are currently attempting to establish the movements of everyone who entered and exited the Omagh housing development where Constable Kerr lived in the days leading up to his murder. They believe this could lead them to the bombers.
The detective in charge of the investigation, Chief Superintendent Raymond Murray, said the booby trap bomb that killed the 25-year-old was made up of 500g of high explosives.
It was inside a plastic box which had been attached under his car.
Mr Murray said it had probably been detonated by a tilt switch, which is set off by movement.
He said police believe the bombers came into the Highfield development where Constable Kerr lived and planted the device some time between Thursday evening and when it exploded on Saturday afternoon outside his home.
“The key to success in this investigation lies in the detail and it lies in the Highfield development where Ronan lived.
“We need to establish the time frame during which the bomb could have been planted at Highfield Close.
“To do this accurately, we need to establish everything that happened in the Highfield development since tea-time on Thursday,” said Mr Murray.
He added: “Police need to chart all movements in and out of the development and identify those who made them.
“That includes residents going in and out, on foot, on a bike, in a car, van or lorry.
“We are working to create a minute-by-minute picture of activity in Highfield. Somewhere in that picture is the bomber. We need the community’s help to identify the killer and their accomplices.”
Components of the bomb are being studied by forensic officers.
Mr Murray said that the bomb also contained a timing mechanism which may have been for the safety of the bombers while they moved the device.
A special phone line, 028 8225 6659, has been set up for residents to make contact with detectives.