Security officials in Afghanistan's Khost Province have impounded a truck loaded with more than three tons of explosives, RFE/RL's Radio Free Afghanistan (RFA) reports.The chief of the Khost City Security Department, Abdulqayum Baqizoy, told RFA that the truck crossed the Afghan-Pakistani border during the night of March 26. He said terrorists planned to use the truck for an attack against a local government building on March 27. He said the truck driver and his accomplices escaped