Two days after explosives were intercepted on a cargo flight out of Yemen, suspicion is falling on a 28-year-old Saudi bomb-maker named Ibrahim Hassan al-Asiri. Not only is he a known al Qaeda affiliate, but he is believed to have killed his own brother last year while attempting to assassinate a Saudi prince. Asiri is also a prime suspect to have built the bomb that a man tried to detonate last Christmas on a flight bound for Detroit. Both devices contained the explosive chemical PETN. "He is certainly someone we are focused on," one U.S. official said. One bomb was concealed in a package mailed from Yemen to a synagogue in Chicago and officials said Saturday that they had apprehended the woman who actually sent it from Sanaa. British officials also specified that the bomb was viable.