Police say four children have died in northwestern Pakistan after they picked up an old ammunition shell that exploded. Police officer Qazi Ataur Rehman says the boys, aged 10 to 13, found the shell at the site of a former Afghan refugee camp in Chitral district and may have wanted to sell it to a scrap metal dealer. The blast happened late Sunday. Rehman says old ordnance has been found at the site before. Chitral lies in Pakistan's mountainous north, near the border with Afghanistan.