CIUDAD VICTORIA, Mexico—Mexican authorities have discovered 652 Central American migrants in six trailers near the United States border. The trucks stopped at a military checkpoint Thursday night on a highway between Ciudad Victoria and Monterrey in the northern state of Tamaulipas. The state public safety agency said Friday that four suspects were arrested. Among the migrants were 564 Guatemalans, as well as migrants from Honduras, El Salvador, Nicaragua, and Belize. More than half of those aboard the trucks were children, nearly 200 of them not accompanied by an adult. Authorities said the trucks’ journey appeared to have started in the central state of Puebla and they were trying to reach Monterrey, a key transportation hub for reaching various points on the U.S.-Mexico border. The trailers were padlocked, forcing authorities to move them to state police facilities to cut them open. The Red Cross said that 40 migrants were evaluated for …