close Video Train carrying migrants stops in Monclova, Mexico A train carrying migrants from Mexico to the U.S. southern border makes a stop in Monclova. Mexican authorities blocked dozens of migrants from hitching a ride to the U.S.on freight trains in Mexico City on Friday in a major new enforcement effort. Thousands of people have used the freight trains, known as" The Beast," to hitch a dangerous ride to the Mexico-U.S. border before they cross over illegally. Earlier this week, the Mexican