In an effort to trace the source of the components, the Explosives Unit at the agency’s state-of-the-art crime laboratory in Quantico, Va., outside of Washington, was comparing the materials collected from sidewalks, rooftops, gutters, overhangs, and even the soles of victims’ shoes against lab reports generated from thousands of previous blasts around the world, looking for a “bomber signature.”

“I think that they should be coming out any day now with the results,” said Representative Michael McCaul, Republican of Texas and chairman of the House Homeland Security Committee.

The efforts parallel those in Boston, where investigators are sifting through thousands of images, including on videos, and eyewitness reports from the Monday attacks.

The methodical work at Quantico is seen as critical in helping investigators identify the perpetrators and secure a conviction in the worst terrorist attack on US soil since Sept. 11, 2001.

“Most bombing investigations like this are forensically driven,” said former supervisory special agent James T. Thurman, who served as chief of the Explosives Unit in the FBI Laboratory’s Bomb Data Center. “Whatever is found that ultimately goes to the laboratory is what drives the investigation and connects a possible subject with the components.”

McCaul, a former prosecutor who has been regularly briefed on the progress of the bombing probe, said he has been told by investigators that they are confident the bomb analysis will provide new information to propel the investigation forward.

“That will release a volume of information in terms of tracing where the gunpowder was purchased [for the bombs], where the ball bearings were manufactured, where the actual [cooking] pot, or device itself, with a serial number, was manufactured and bought,” he said. “From there they can look at possible search warrants.”

McCaul plans to visit Boston on Friday to huddle with local authorities.

An FBI spokeswoman in Quantico, Ann Todd, said agency officials could not be made available Thursday for interviews about the lab’s procedures, “in deference to the ongoing investigation being conducted by law enforcement authorities in Boston” and to avoid “unintended challenges for investigators during the early stages of this investigation.”

But those familiar with the inquiry and the FBI’s lab said the Explosives Unit is relying on specialized tools to conduct what amounts to an autopsy on the pair of so-called IEDs — improvised explosive devices — that were apparently detonated by battery-powered timers near the Copley Square finish line.

One is a database known as the Explosive Reference Tool, a searchable computer archive containing investigation reports from bombings dating back decades, along with so-called underground bomb-making handbooks and manufacturing data for key bomb-making components and explosives.

According to one former FBI explosives expert, the findings also will be compared with thousands of research reports from IED attacks overseas to determine if the Boston bomb makers could have received foreign training.

That part of the investigation will be handled by the Terrorist Explosive Device Analytical Center, a separate outfit at Quantico established in 2004 “to gather and share intelligence about these devices — helping to disarm and disrupt IEDs, link them to their makers, and most importantly, to prevent future attacks.’’

“Having the database from Iraq and Afghanistan and other bombing events around the world is critical,” said K. Jack Riley, vice president of the national security division at the government-funded Rand Corp., which has advised the Pentagon in its multibillion dollar effort to counter roadside bombs on the battlefield, the biggest killer of US troops.

The government also has a trove of data from domestic bombings. While most are relatively small and don’t make national headlines, hundreds of episodes involving so-called incendiary devices — such as pipe bombs — take place each year in the United States, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.