The White House was locked down on Tuesday night, as authorities investigated what appeared to be a smoke bomb that was tossed over the compound's fence.<br/> The device was thrown as about 1,000 "Occupy DC" protesters were demonstrating outside the presidential residence, according to a Secret Service spokesman.<br/> The protesters had gathered earlier at the Capitol building, and marched down Pennsylvania Avenue, with a brief stop at the Supreme Court.<br/> The majority of demonstrators were quickly cleared from the area, and no arrests were made.<br/> President Barack Obama and his wife Michelle had gone out to dinner to celebrate the First Lady's birthday, and were not at the White House during the incident.<br/> Travis Brecher, Reuters
