Portion of Downtown Boston Remains Closed After Bombing

Investigators combing through photos and videos of bombing for evidence

A large area of downtown Boston remained cordoned off by police today as authorities pursued an investigation into the two bombs that exploded at the finish of the Boston Marathon Monday, killing three people and wounding more than 100.

A stretch of Boylston Street and the blocks around it were closed to traffic as police searched for evidence of the identity of who placed the bombs packed with ball bearings to maximize casualties.