Investigators found "shredded pieces of pressure cookers" in the bomb debris, Fox reported, adding that a source said it was hidden inside a black backpack placed in a garbage can. The FBI is hoping to identify the cellular telephone which may have been used to trigger the bomb.
If the reports prove to be true, they could tie the attack to Islamist terrorists. Pressure cooker bombs are among the suggestions for terrorist attacks offered by al-Qaida's Inspire magazine. An article entitled "Make a Bomb in the Kitchen of Your Mom" is strikingly similar to what is known about Monday's attack that killed three people and injured more than 130 others gathered near the marathon's finish line.
Pressure cooker bombs should be "placed in crowded areas and left to blow up. More than one of these could be planted to explode at the same time. However, keep in mind that the range of the shrapnel in this operation is short range so the pressurized cooker or pipe should be placed close to the intended targets and should not be concealed from them by barriers such as walls."
A 2010 release from the Department of Homeland Security said pressure cookers "frequently have been used in Afghanistan, India, Nepal, and Pakistan. Pressure cookers are common in these countries, and their presence probably would not seem out of place or suspicious to passersby or authorities."
At least two previous terror plots in America included pressure cookers. One of the explosives Faisal Shahzad left in Times Square was a loaded pressure cooker, the DHS release said. And in 2011, Army Pvt. Jason Naser Abdo told investigators he planned to pack gun powder and shrapnel into pressure cookers as part of an attack on a restaurant popular with personnel from Fort Hood. When he was arrested, Abdo had a copy of Inspire magazine and explosive supplies and two pressure cookers.