Police Still Searching for Leads After Boston Marathon Bombing

Hagel calls bombing a 'cruel act of terror'; Boston-area apartment focus of investigation, but no suspects are yet in custody; Massachusetts governor says no additional bombs found on scene.

U.S. President Barack Obama on Tuesday called the bombings that killed three andwounded more than 170 people at the Boston Marathon a day earlier an "act of terror," but said it was not clear yet whether the twin blasts were the work of a foreign or domestic group or a "malevolent individual."