HANOI, Jan. 3 (Xinhua) -- A big explosion occurred in Vietnam's northern Bac Ninh province early Wednesday morning, killing two kids and injured six people, provincial authorities announced.

The accident at a house of a scrap collector in Van Mon commune, Yen Phong district also destroyed two houses and damaged many others within a 500 meters radius from the explosion. At the scene, some bullets have been found.

Many households in Van Mon specialize in collecting and processing scraps which sometimes include unexploded ordnance such as mortar shells, mines and bullets.

During the 1965-1975 Vietnam War, the U.S. Armed Forces deployed more than 15 million tons of bombs, mines, artillery shells and other ordnance in Vietnam, in which 10 percent did not detonate as designed, according to the Vietnam Veterans Memorial Fund of the United States.

Vietnamese scrap collectors often saw unexploded ordnance for metal and explosive, while small children play ammunitions by breaking them, resulting in hundreds of deaths and injuries annually.