BAGHDAD, Iraq, April 14 - Investigators have discovered several mass graves in southern Iraq that are believed to contain the bodies of people killed by Saddam Hussein's government, including one estimated to hold 5,000 bodies, Iraqi officials say. The graves, discovered over the past three months, have not yet been dug up because of the risks posed by the continuing insurgency and the lack of qualified forensic workers, said Bakhtiar Amin, Iraq's interim human rights minister. But initial excavations have substantiated the accounts of witnesses to a number of massacres. If the estimated body counts prove correct, the new graves...