Authorities in the Mexican state of Chiapas have discovered 500 migrants crammed into the trailers of two U.S.-bound trucks. The migrants lacked food and water and had only holes punched into the floor of the trucks for air; they clung to nets to maintain their balance. Most of the immigrants are believed to be from Guatemala, though there were some from Ecuador and El Salvador as well. They are believed to have paid $7,000 each. Four people have been arrested.