NEW : The municipal police chief said the stampede , which began around 10 p.m. , likely occurred because a suspension bridge packed with people began to sway , creating panic , said Philip Bader , a news editor with the Phnom Penh Post newspaper . An additional 20 people are reported injured at an annual ceremony . Cambodia has declared this a national day of mourning . The explosion occurred on a bridge during an annual ceremony to honor naval forces .
NEW : An additional 20 people are reported injured at an annual ceremony . Cambodia has declared this a national day of mourning . The explosion occurred on a bridge during an annual ceremony to honor naval forces .