DENVER - A federal source tells CALL7 Investigators that un-detonated bombs or bomb fragments found along the course of the Boston Marathon could yield critical clues that lead to the assailant.
Two explosions rocked the finish line of the Boston Marathon around 2:50 p.m. Eastern Standard Time, killing at least two people, leaving dozens more injured, according to preliminary reports.
Investigators are tasked with searching through a massive area, searching for other bombs that didn't go off as well as for fragments of exploded devices. So far two other devices of an unknown type have been located, according to The Associated Press.
That evidence could yield important clues because bomb-makers tend to have signature methods in their construction. The materials used in the bombs, if identified, could also lead to suppliers and possibly to the bomb-maker who obtained them.
Video and still images suggest the explosives were from a low-ordnance device that produced a low-pressure explosion, sources tell CALL7 Investigators. However, those sources caution that their analysis is speculative and all possibilities are open as the investigation moves forward.
Authorities are expected to conduct hundreds of interviews with the injured and witnesses.
Some agents theorize the attack could be linked to a specific cause, but ideas are at the moment purely speculative.
The bombings have led officials elsewhere in the country to elevate security, including in New York City and Washington, D.C.
Colorado law enforcement agencies are monitoring for any suspicious activity following events in Boston. A statewide alert from the Colorado Information Analysis Center came within an hour and half of the bombings.