Looters unleashed last year by the U.S.-led invasion of Iraq overran a sprawling desert complex where a bunker sealed by U.N. monitors held old chemical weapons, American arms inspectors report. Charles Duelfer's arms teams say all U.N.-sealed structures at the Muthanna site were broken into. If the so-called Bunker 2 was breached and looted, it would be the second recent case of restricted weapons at risk of falling into militants' hands. Officials are unsure whether this latest episode points to a threat of chemical attack, since it isn't known if usable chemical warheads were in the bunker, what may have...