The crude explosive devices used against runners and spectators at the Boston Marathon were similar to the kitchen pot bombs aimed at U.S. troops on foot patrol in Afghanistan, law enforcement and Congressional officials said Tuesday.
For nearly 10 years, presidential directives, Homeland Security Department reports and local law enforcement officials have warned of the eventual threat within the U.S. of “pressure cooker” bombs developed by terrorists in Afghanistan and Iraq.
After briefings from law enforcement and U.S. intelligence officials, Rep. Randy McCaul (R-Tex.) said that the two devices which detonated in Boston appeared to be “pressure cooker” bombs. Law enforcement officials later confirmed that the investigation was proceeding on the basis that the devices were “pressure cooker” bombs.
But Rick DesLaurier, the FBI’s special agent in charge in Boston, stressed that “the investigation is in its infancy.” At a news conference in Boston, DesLauriers said there had thus far been “no claims of responsibility and the range of suspects and motives is wide open.”
DesLauriers asked the public to contact authorities if they knew anyone who had recently expressed a special “interest in research in how to create explosive devices.”
In Afghanistan, Taliban operatives who lacked the wherewithal or expertise to build “improvised explosive devices” capable of destroying the huge, V-shaped hull MRAPs (Mine Resistant Ambush Protected vehicles) turned to “pressure cooker” bombs as anti-personnel devices. They would be placed along paths expected to be used by U.S. troops on foot patrol.
In the summer of 2011, explosives specialists from the 2nd Battalion, Eighth Marines, showed several of the devices they had found and defused to an embedded reporter. One of the devices had even been placed in a tree, the specialists said.
The terrorists would take a simple kitchen pot, a pressure cooker was preferred, pack it with ammonium nitrate and metal filings, nails and even rocks to increase the lethality, and rig the device to detonate by wire or by a remote device, sometimes a garage door opener.
When triggered, the blast would seek the path of least resistance and most of the force and the debris would blow out the top of the pressure cooker, in effect acting much like a military “shaped” charge that concentrates the force of an anti-tank shell.
As far back as 2004, a Homeland Security Department memo warned of the pressure cooker bomb threat, calling it "a technique commonly taught in Afghan terrorist training camps."
"Typically, these bombs are made by placing TNT or other explosives in a pressure cooker and attaching a blasting cap at the top of the pressure cooker," the memo said.
The attraction of the pressure cooker bomb for the terrorist is that they are cheap, relatively easy to make, and lethal.
A presidential directive on homeland security in 2007 warned that “The threat of explosive attacks in the United States is of great concern considering terrorists’ability to make, obtain, and use explosives, the ready availability of components used in IED construction, the relative technological ease with which an IED can be fashioned, and the nature of our free society.”
In 2010, a joint FBI and Homeland Securty intelligence report issued in 2010 warned that "Placed carefully, such devices provide little or no indication of an impending attack.”
Two years ago, “Inspire,” the online magazine of Al Qaeda in the Arabian, published an article on how to make a pressure cooker bomb. The title of the article was “How To Make A Bomb In The Kitchen Of Your Mom.”