Mexico said it was working to improve security in the border region but suggested the U.S. State Department had overreacted by renewing a warning to U.S. travelers about drug violence in northern Mexico. As with the original travel advisory, the repeat warning on Tuesday angered Mexicans. The update blamed the continuing violence in Mexican border cities on turf battles between drug gangs but noted that was in part the result of Mexico's success in locking up cartel leaders. "Imprecisions and generalizations that hurt the spirit of cooperation in law enforcement and the fight against organized crime should be avoided," the...