For education and discussion only. Not for commercial use. MEXICO CITY - Mexico's top diplomat suggested Thursday that American soldiers disguised as Mexican troops may have been in the military-style Humvee filmed earlier this week protecting a marijuana shipment on the border. Foreign Secretary Luis Ernesto Derbez also told a news conference that U.S. soldiers had helped drug smugglers before. However, he offered no evidence. The U.S. Embassy in Mexico made no immediate comment on Derbez's claims. His comments came a day after U.S. Ambassador Tony Garza issued a statement asking the Mexican government to "fully investigate" the border incident....