Explosions near Boston Marathon finish line hours after winners crossed finish line

From USAToday:

At least three death and many injuries were reported Monday after two explosions ripped through the crowd near the finish line of the Boston Marathon.

Fox News quoted a law enforcement source as saying at least three people had died. The Boston Herald reported at least a dozen injuries.

Authorities have not identified the cause or source of the explosions.

Witnesses said the blasts occurred in quick succession about 2:50 p.m. on Boylston Street near the intersection of Exeter Street, three hours after the winner had crossed the finish line. Some store fronts were blown out.

UPDATE:  MSNBC is reporting that two additional devices have been found and dismantled. A third explosion almost an hour later occurred at the JFK  Library in Boston.