WASHINGTON (AP) - The chief of the U.S. Africa Command is telling Congress that thousands of shoulder-fired anti-aircraft weapons from the arsenal of deposed Libyan leader Moammar Ghadafi remain unaccounted for in Africa and beyond. Army Gen. Carter Ham tells the Senate Armed Services Committee some of those weapons, as well as explosives and other arms once under Ghadafi's control, have fallen into the hands of extremists in northern Mali. He says others have spread to rebel groups in Syria. The Ghadafi regime was overthrown in 2011. Ham said at a hearing Thursday that he could not discuss details in public. But he did say that a U.S. government effort to buy back portable anti-aircraft weapons from Libya has had only "modest success."