Police find circuit board connected to Boston attack

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The Boston Globe reports that investigators have found a circuit board that's believed was used to detonate two bombs that exploded Monday during the Boston Marathon.

The bombs, detonated about 12 seconds apart, killed three people and injured 176 others, including 17 who are still in critical condition. The attacks created a scene of bloody carnage near the finish line of a race that is a colorful rite of spring and draws runners from around the world.

The Globe also reports that components of the bombs have been recovered. Two people briefed on the investigation tell The Associated Press that a pair of bombs packed into pressure cookers and concealed in duffel bags blew up within seconds of each other.

Massachusetts Governor Deval Patrick and other dignitaries had been sitting in the viewing stands just across from where the first explosion occurred, although the governor was not there at the time of the blast. Another bomb was placed about 100 yards away in the 700 block of Boylston Street.

The explosives used in the Boston Marathon bombing were crude devices often called pressure cooker bombs, according to a person briefed on the investigation.

The person spoke on condition of anonymity because the investigation in Boston was still ongoing.

While the devices have been frequently used in Afghanistan, India and Pakistan, in recent years they have also shown up in plots in the U.S. and France.

Explosives typically are placed inside a pressure cooker - a commonplace cooking utensil in many countries - and the device is then detonated using everyday electronic equipment such as digital watches, garage door openers, cellphones or pagers. Pressure builds inside the container and shrapnel is expelled. Al-Qaida affiliates have provided training and manuals on how to build such devices.