More than 1,000 law enforcement officers from different agencies have been assigned to the investigation, which includes meticulously scouring through wreckage and debris, interviewing hundreds of witnesses and poring over thousands of videos, phone records, photographs and websites.
"There's a lot of data and that's part of the challenge," Ray Boisvert, a former assistant director of intelligence at CSIS, told CBC News. "They'll have a very big time ahead of trying to sort out all the small pieces of debris at the site and they will have to combine that with trying to deconstruct all the available data, and that includes videos, phone conversations, contacts e-mails social media and so on."
"You have to know how to sort through it and to not get too distracted or go down the wrong rabbit hole."
Pepperdine University law professor Greg McNeal, who is also a national security specialist, wrote in Forbes.com that the investigative team will include forensic specialists, medical examiners, photographers, structural engineers, bomb disposal technicians and analysts, sketch artists, and others looking for and collecting evidence.
'Difficult task for investigators'
"Given the size of the crime scene(s) and the number of witnesses, collecting evidence and preserving it will be a difficult task for investigators," he said.
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The investigation has already recovered several items, including pieces of black nylon that could be from a backpack, and what "appear to be fragments of BBs and nails possibly contained in a pressure cooker device."
Former FBI special agent Donald Borelli told MSNBC News that trying to put together the devices that exploded is an important part of the case.
"Collect any little bits and pieces, wire, anything that can help put the device together and figure out what it looked like before it blew up," Borelli said.
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He added that explosive material carries a signature, meaning investigators may be able to identify the manufacturer.
Richard Clarke, a former White House counter-terrorism adviser, said the FBI will try to determine if a bomb design was used based upon a specific "how to make a bomb" web page on the internet.
"Law enforcement authorities will try to determine where the bomb materials and the back pack or other carrying case were purchased," Clarke wrote in a piece for ABC News.
Investigators must also seek out all the witnesses, which includes those who came forward with evidence, and those who may have fled or were transported from the scene, McNeal said.
"Victim and witness statements are often times essential pieces of evidence in establishing the circumstances of the incident, potential perpetrator, and the nature of the device," he said.
'Phone records scoured'
Phone records will also be scoured, Clarke said, adding that it may be possible to determine what phone numbers were used to trigger the blasts if the bombs were detonated by mobile phones. He said the FBI will look at calls that went through specific cell towers in the area.
Sifting through all the videos and photographs taken before, during and after the bombings will also be key.
"As they study this footage they may also look for people who were behaving suspiciously or who didn't seem surprised by the event," McNeal said.
Investigators will also examine all the faces of people in the area at the time of the blasts, Clarke added.
"They will try to put names to those faces, using facial recognition matching software, drawing on drivers license, passport, and visa databases," Clarke wrote in piece for ABC News.
But Boisvert cautioned that may not immediately lead law officials to a suspect.
"There will be a lot of people in that environment and there will be a lot of persons only partially identified. So it will take a lot of investigative knocking on doors," he said.Suggest a correction