Few clues have been announced in the investigation of the Boston Marathon bombing, and several former law enforcement officials spoke about what the evidence may—or may not—mean.
Investigators said the two bombs were likely made out of pressure cookers packed with shrapnel to make them more deadly.
Here's what some experts told CNBC on Wednesday about the evidence.
(Read More: Boston Bombs Believed Packed in Pressure Cookers)
Clint Van Zandt, former FBI profiler and NBC analyst, described on "Squawk Box" what authorities know about the bombs. "We know that authorities have found the lid to one of the pressure cookers on top of a nearby building. In essence the force was so great that it blew it off and blew it on top of the building."
"One of the two devices that's been called a pressure cooker, it was 6 liters," he said. "Now that's interesting because in the U.S. we'd call that one and a half gallons. But here's something that says 6 liters. That could suggest the pressure cooker had been made internationally."
Clark Kent Ervin, former inspector general of the Department of Homeland Security, said the bombs were crude devices, but added: "The simultaneity of the attacks, the iconic nature of the venue ... the fact that lots of people were gathered there. The fact that the bombs were apparently designed to maim people. All of this suggests to me an al Qaeda-inspired attack."
"The pressure cookers are commonly used throughout South Asia, the Middle East, North Africa," he continued. "So that's a further indication to me this is the kind of suspect we might be looking at now."
Although it may have been inspired by al Qaeda, he concluded: "My bet is we'll find out a single individual is responsible for this."
(Slideshow: Scenes From the Boston Marathon Bombing)
Philip Mudd, former deputy director of the CIA's Counterterrorist Center, said the attack does not have the hallmark of international terrorism because the marathon is not a globally iconic venue.
"My initial response having done this stuff for 20 years in government is it tells us more about who did not do this," he said. "I'm not sure who did it, but I don't think it's the guys I watched for 20 years."
Mudd, also a former senior FBI intelligence adviser, described how authorities process leads in this type of investigation. "Any time, any threat came into the bureau when I sat there at the morning threat briefing, I don't care if it was somebody who said, 'Grandma's got a nuke under the bed,' we're going to chase it down."
Sen. Angus King, Independent from Maine and a member on the Intelligence and Armed Services committees, told CNBC, "Anybody that was there that has pictures of somebody finishing or standing in front of the finish line or in that area, chances are somewhere out there in America today on somebody's iPhone is a picture of the bomber."