NBC's Pete Williams discusses how an ordinary stove-top pressure cooker can be turned into a dangerous — and deadly — IED, similar to the what is being eyed in the Boston Marathon blasts.
Pressure cooker bombs like the ones authorities believe were used at the Boston Marathon have been used in attacks around the world for almost 40 years. Just two months ago, one exploded in a restaurant in Afghanistan, killing five people.
Other attacks or plots involving a souped-up version of this ordinary piece of kitchen equipment, typically loaded with explosives and shrapnel and then detonated. include:
-- On Sept. 10, 1976, a Croation nationalist put one in a locker at New York City's Grand Central Terminal, killing one NYPD officer and wounding another as they tried to dismantle it.
-- A July 11, 2006, coordinated attack on the Mumbai transit system used pressurized cooking pots loaded with the explosive RDX and ammonium nitrate. More than 130 people were killed in a wave of bombings targeting first-class compartments in seven trains.
-- A bombing attempt in Times Square on May 1, 2010, featured a pressure cooker packed with fireworks as the primary charge. It went off, but the main bomb inside the suspect's vehicle did not detonate.
-- In 2011, U.S. Army Private Naser Jason Abdo was charged with a plan to blow up Fort Hood troops and a pressure-cooker with smokeless gunpowder was found in his motel room.
"Recipes" for pressure cooker bombs also have appeared in white supremacist literature for 40 years, say counterterrorism experts. And they have been used for more than 30 years overseas in various civil wars and as improvised explosive devices against U.S. troops.
More recently, extremist Muslim jihadists have posted instructions on how to make them. Last month, Al Qaeda in the Arabian Peninsula included an article titled, "Make a Bomb in the Kitchen of your Mom," in the latest edition of its "INSPIRE" Magazine propaganda. The article, reprised from INSPIRE's first edition in July 2010, included detailed, illustrated instructions on making pressure cooker bombs.
Investigators say pressure cookers packed with shrapnel were used in the Boston attack. NBC News' Jay Gray reports.
House Homeland Security Committee Chairman Michael McCaul, R-Texas, said a timer can be attached to the cooker and set in advance to go off after the bomber has left the area, or it can be detonated remotely by cell phone.
In the latter instance, he said, investigators may have an important thread to follow -- any cell phone calls made in the area at the moment of the blast.
A 2004 bulletin by the Department of Homeland Security, which was posted on a Coast Guard auxiliary website, said the conversion of pressure cookers into improvised exposive devices "is commonly taught in Afghan terrorist training camps."
However a wide variety of groups, including Maoist rebels, have used them, the bulletin said.
Law-enforcement officials stress that they have not determined whether the marathon blasts were the work of domestic or international assailants, a single attacker or a terrorist group.
NBC News' Pete Williams, Richard Esposito and Robert Windrem and the Associated Press contributed to this report.
Related story: Bomb type gives first clue on path to perpetrator