By Steve Neavling
ticklethewire.com
The explosions at the Boston Marathon were caused by pressure cooker bombs stuffed with shrapnel and inflammable material, the Associated Press reports.
Those devices are popular in Afghanistan, India and Pakistan, and recently were discovered in plots in the U.S., the AP wrote.
Typically, would-be bombers pack the inside with shrapnel and an inflammable material and detonate them with cell phones or timers.
USA Today also reported that instructions on making the bombs were published two years ago in Inspire, an online magazine with ties to al-Qaeda.
