FILE - In this April 18, 2012 file photo, birds fly in the foreground as a plume of ash and steam rises from Popocatepetl volcano as seen from San Andres Cholula, Mexico, Wednesday, April 18, 2012. The volcano continues to shoot ash into the sky southeast of Mexico&#39;s capital, and television images on Friday, April 20, show a reddish glow near the crater. (AP Photo, File)