A child walks under a shelter in Santiago Xalitzintla, which is the nearest village to the Popocatepetl volcano, in Mexico's Puebla, on April 17, 2012. Mexican Interior Minister Alejandro Poire said Tuesday that the country is keeping a close watch on the Popocatepetl volcano near Mexico City. [Xinhua]

A woman sits in Santiago Xalitzintla, which is the nearest village to the Popocatepetl volcano, in Mexico's Puebla, on April 17, 2012. Mexican Interior Minister Alejandro Poire said Tuesday that the country is keeping a close watch on the Popocatepetl volcano near Mexico City. [Xinhua]

A man holds a mask in Santiago Xalitzintla, which is the nearest village to the Popocatepetl volcano, in Mexico's Puebla, on April 17, 2012. Mexican Interior Minister Alejandro Poire said Tuesday that the country is keeping a close watch on the Popocatepetl volcano near Mexico City. [Xinhua]

Children wearing masks play in Santiago Xalitzintla, which is the nearest village to the Popocatepetl volcano, in Mexico's Puebla, on April 17, 2012. Mexican Interior Minister Alejandro Poire said Tuesday that the country is keeping a close watch on the Popocatepetl volcano near Mexico City. [Xinhua]

A rescuer gives masks to children in Santiago Xalitzintla, which is the nearest village to the Popocatepetl volcano, in Mexico's Puebla, on April 17, 2012. Mexican Interior Minister Alejandro Poire said Tuesday that the country is keeping a close watch on the Popocatepetl volcano near Mexico City. [Xinhua]