AP: Explosives Used in Bombings Contained in 'Pressure Cookers' and Placed in Duffel Bags -- Same Type Described in How-To Section of Al-Qaeda Mag

Edior's note: TheBlaze has decided not to excerpt the full al-Qaeda article on how to make a "pressure cooker" bomb or even link to it. There are key parts of the "Inspire" article that we have intentionally left out.

The cover for the article "How to make a bomb in the kitchen of your mom," which described how to make "pressure cooker" bombs like the ones sources tell the AP were used in Boston.

WASHINGTON (TheBlaze/AP) -- The explosives used in the deadly Boston Marathon bombing were contained in 6-liter pressure cookers and hidden in black duffel bags on the ground, a person briefed on the investigation told The Associated Press on Tuesday.

One of the explosives contained shards of metal and ball bearings, and another contained nails, the person said.

A second person briefed on the investigation confirmed that at least one of the explosives was made out of a pressure cooker. Both spoke on condition of anonymity to discuss an ongoing investigation.

"Pressure cooker" bombs have been in the news before. As the Christian Science Monitor noted in July 2011, when Army Pfc. Naser Abdo was caught plotting to blow up Ft. Hood, he was caught with plans to make such bombs -- instructions he got from an al-Qaeda magazine.

A soldier suspected of plotting a bomb and handgun attack against military personnel at Fort Hood, Texas, was using a bombmaking recipe from an Al Qaeda-linked online magazine, according to federal court documents released on Friday.

Army Pfc. Naser Jason Abdo has been charged with possession of an unregistered destructive device and ordered held without bond. At the time of his arrest on Wednesday, law-enforcement officials recovered a handgun, assorted bombmaking materials, and an article entitled, “Make a bomb in the kitchen of your Mom.”

[...]

According to the FBI affidavit, at the time of his arrest by the Killeen Police Department, Abdo was carrying a backpack. In addition to the bombmaking article, it contained two clocks, two spools of wire, Winchester .40 caliber ammunition, and a Springfield .40 caliber handgun. He was also carrying a composition notebook with a list that included: “red black green wire; 9v bat, Christmas lights; pressure cooker; power drill; 160 gunpowder; gorilla tape; motal epoxy, glue; 1 small box of shotgun shells; cardboard box; gloves.”

Police and federal agents later searched his hotel room – No. 230 at America’s Best Value Inn and Suites in Killeen. Among items seized: “electric drill; two clocks; six bottles of smokeless gunpowder; five cut shotgun shells; three Springfield ammunition magazines; four razorblades; shotgun pellets; and two pressure cookers.”

According to the affidavit, Abdo was questioned by law-enforcement officials shortly after his arrest and confirmed his intention to carry out an attack.

“Abdo admitted that he planned to assemble two bombs in the hotel room using gun powder and shrapnel packed into pressure cookers to detonate inside an unspecified restaurant frequented by soldiers from Fort Hood,” the affidavit says.

These types of pressure cooker explosives have been used in Afghanistan, India, Nepal and Pakistan, according to a July 2010 joint FBI and Homeland Security intelligence report. One of the three devices used in the May 2010 Times Square attempted bombing was a pressure cooker, the intelligence report said.

"Placed carefully, such devices provide little or no indication of an impending attack," the report said:

This Homeland Security Department pamphlet, from July 2010, distributed to police, fore, EMS and security personnel shows a diagram for rudimentary improvised explosive devices (IEDs) using pressure cookers to contain the initiator, switch and explosive charge. A person briefed on the Boston Marathon investigation says at least one of the explosives were in 6-liter pressure cookers and placed in black duffel bag. (AP Photo/Homeland Security Department)

The Pakistani Taliban, which claimed responsibility for the 2010 attempt in Times Square, has denied any role in the Boston Marathon attack.

Below is the page from the Summer 2010 edition of "Inspire" and the article "How to Make a Bomb in the Kitchen of Your Mom" -- it explains to attach shrapnel to the device and place it in a container such as a pressure cooker because the bomb is a "mechanical one" that uses built-up pressure to explode:

A page from the al-Qaeda magazine "Inspire" explaining how to make a homemade "pressure cooker"-type bomb.

Another page from al-Qaeda's "Inspire" magazine explaining how to make a "pressure cooker" bomb, the same type sources now tell the AP was used in the Boston Bombings.

The article goes on to explain how to make the bomb by using the material extracted from match heads as the ignition source.

Law enforcement has not yet determined what was used to set off the explosives. Typically, these bombs have an initiator, switch and explosive charge, according to a 2004 warning from the Homeland Security Department about these types of explosives.

"We will go to the ends of the Earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice," said Richard DesLauriers, FBI agent in charge in Boston.

Investigators in Boston are combing surveillance tapes and pictures from Monday.

Naser -- the Army Pfc. who plotted against Ft. Hood -- was convicted and received two life sentences in August 2012.