MEXICO CITY - Mexican agents arrested a former medical student who seized control of the remnants of the Juarez cartel, the country's attorney general said Monday, shedding light on a split within what was once Mexico's most powerful cocaine smuggling gang. Ricardo Garcia Urquiza, captured in a shopping mall in Mexico City on Nov. 11, is accused of overseeing an organization that moved up to 5 tons of Colombian cocaine a month into Mexico and on to the United States. Attorney General Daniel Cabeza de Vaca said that since late 2004, Garcia Urquiza was responsible for as much as 20...