WASHINGTON — The bomb investigators swarming Boston are combining high-tech tools with old-fashioned shoe leather as they piece together what blew up and why.
A special federal bomb squad has mobilized, joining state and local counterparts in a search for everything from the shrapnel that slashed victims to the residue left behind after dual blasts Monday killed three and injured more than 170 near the finish line of the Boston Marathon. It’s painstaking work, combining chemistry, computer databases and sheer doggedness.
Richard DesLauriers, special agent-in-charge of the bureau’s Boston division, appealed to the public late Tuesday to produce any information about anyone seen carrying a dark heavy bag at the scene of the bombing or who threatened an attack on the Boston Marathon. He also sought information about explosions heard in remote areas where the bomber might have conducted tests.
“We are doing this methodically, carefully, yet with a sense of urgency,” he said.
“Someone knows who did this. Cooperation from the community will play a crucial role in this investigation.”
Gene Marquez, acting special agent-in-charge of the Bureau of Alcohol, Tobacco, Firearms and Explosives’ Boston field office, said that the bombing scene would take “several days to process.”
Some clues come from what doctors pull from the victims’ bodies. Doctors on Tuesday reported that they have been extracting objects that appeared to be pellets and nails from the legs and torsos of victims, a possible sign that the two bombs that exploded Monday had been destructively packed.
A former senior U.S. government official who was briefed on the investigation but declined to be identified because of the sensitivity of the information, confirmed for McClatchy Newspapers that the bomb was put into a pressure cooker, a tactic that counterterrorism agencies have found in the past in jihadist plans and “recipes.”
No one has claimed credit for the bombings.
Following an Oval Office meeting Tuesday with President Barack Obama and his top national security advisers, Homeland Security Secretary Janet Napolitano said there was no evidence that the bombings were part of a broader scheme.
Among the lines of inquiry are that the attack was the work of domestic terrorists or a lone wolf, said a person familiar with the investigation, who also asked for anonymity because of the sensitive nature of the information.
The Department of Homeland Security issued a bulletin around 2005 warning of the risks of pressure cookers in explosive devices after recovering jihadist literature describing the tactic.
“We have only two devices that we are aware of and both were the devices involved in the damage and explosive incidents,” Marquez said, responding to reports Monday that additional devices had been found.
An often politically embattled part of the Justice Department and periodically targeted for elimination by conservatives, the Bureau of Alcohol, Tobacco, Firearms and Explosives, still known as the ATF, is playing a crucial but subordinate role in the investigation. The FBI, an occasional bureaucratic rival that’s also part of the Justice Department, is the lead agency.
DesLauriers said Tuesday that the bureau and the multi-agency Joint Terrorism Task Force with which it’s working have received “voluminous tips” since the explosion. Boston Police Commissioner Edward Davis III said that the blast area is “the most complex crime scene in the history of our department.”
About 30 ATF investigators are on the scene, including members of what’s called the National Response Team, called up to aid the Boston Police Department’s bomb squad. The national team includes special agents, forensic chemists, canine handlers and bomb technicians, known as explosives enforcement officers. They deploy from a fleet of white-and-blue trucks loaded with specialized equipment and have previously been called up for manmade catastrophes, including the April 1995 Oklahoma City bombing.
The turf and personality clashes that can sometimes shadow other joint investigations are eased, veteran investigators say, by the fact that every bomb technician from every civilian agency has graduated from the same Hazardous Devices School, run jointly by the Army and the FBI at Redstone Arsenal in Huntsville, Ala.
“When we go on the scene, we’re working side by side with people who went to the same school,” said Barney Villa, an independent security consultant and former bomb squad member in the Los Angeles County Sheriff’s Department. “We all have mutual respect for each other.”
The investigators picking through the Copley Square crime scene that by Tuesday had shrunk from 15 blocks to 12 will have photographed and recorded every potential piece of evidence, Villa explained. Everything gets tagged and is assigned a number, and then is typically brought back to a lab for closer scrutiny. Analysts test for chemical residue. Closed-circuit TV and homemade videos are played and replayed to observe blast patterns.
The information collected can be compared to the 185,000-plus arson and explosive incident reports stored in the U.S. Bomb Data Center, the largest database of its kind in the world. Through a Bomb Arson Tracking System, in which records are classified as “sensitive but unclassified,” investigators can match findings and search for patterns.
“One (goal) is a forensic examination of the debris at the scene in an attempt to collect and ultimately reconstruct the design of the devices themselves,” explained Brian Jenkins, a longtime counterterrorism expert and senior adviser to the president of the RAND Corp., a nonprofit global policy think tank. “The explosive residue will tell us some things about what kind of explosives were used, and where they might have been acquired.”
Remnants of the bomb, Jenkins added, might show what kind of pressure cooker was used, and hence where it was sold. Cellphone debris will be closely examined for signs of residue, as a potential clue that the phone might have been used for detonation.
“A lot of these leads won’t turn out,” Jenkins said, adding that tips from the public are often “low yield.”