By Laura Gottesdiener and Lizbeth Diaz CIUDAD JUAREZ, Mexico (Reuters) - Mexican authorities have begun constructing giant tent shelters in the city of Ciudad Juarez to prepare for a possible influx of Mexicans deported under U.

"It's unprecedented," said Ciudad Juarez municipal official Enrique Licon as workers unloaded long metal bracings from tractor trailers parked in the large empty lot yards from the Rio Grande in order to build a tent city for deportees from the United States.