VIENNA, Austria - The U.N. nuclear agency said Thursday it warned the United States about the vulnerability of explosives stored at Iraq (news - web sites)'s Al-Qaqaa military installation after another facility — Iraq's main nuclear complex — was looted in April 2003. Melissa Fleming, a spokeswoman for the International Atomic Energy Agency, told The Associated Press that U.S. officials were cautioned directly about what was stored at Al-Qaqaa, the main high explosives facility in Iraq. Some 377 tons of high explosives — HMX and RDX and PETN — are now missing from the facility, and questions have arisen about...