Police in Tennessee said a person using a metal detector made an unexpected and startling discovery -- an unexploded mortar round dating from World War II. The Lebanon Police Department said a resident with a metal detector discovered the live mortar Monday behind Hartmann Plantation and alerted authorities. Police summoned the Tennessee Highway Patrol's bomb squad and personnel from Fort Campbell to the scene, and the experts confirmed the mortar was still live. The bomb squad determined the mortar was too unstable to move, so it was safely detonated at the scene. Experts said the mortar was likely left over from when the area was used as a training ground during World War II. The area was searched for more explosives before authorities cleared the scene.