BOSTON (AP) -- Federal authorities are looking for suspects and a motive in the bombings that killed three people and injured more than 140 at the Boston Marathon finish line.
The two bombs that exploded on Monday left the crowded streets full of dazed, bloody victims and raised concerns that terrorists had struck again on U.S. soil.
[SPECIAL COVERAGE: BOSTON MARATHON TERROR ATTACK
President Barack Obama says those responsible will feel "the full weight of justice."
A senior U.S. intelligence official tells The Associated Press that as many as two unexploded bombs were found near the end of the course as part of what appeared to be a well-coordinated attack. The official spoke on condition of anonymity because of the continuing investigation.
The Pakistani Taliban have denied any role in the bombings.