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General view of two ambulances at the San Nicolas de los Ranchos community near Popocatepetl volcano, in Puebla, Mexico, on May 12, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Jose Castañares/AFP/Getty Images ( 519676282 )

Clouds of ash and smoke are spewed from the Popocatepetl Volcano as seen from Santiago Xalitxintla, in Puebla, Mexico, on May 13, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Ronaldo Schemidt/AFP/Getty Images ( 519697644 )

View of Santiago Xalitxintla community with the Popocatepetl Volcano on the background, in Puebla, Mexico, on May 13, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Ronaldo Schemidt/AFP/Getty Images ( 519698167 )

A family walks in Santiago Xalitzintla community near Popocatepetl volcano, in Puebla, Mexico, on May 13, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Ronaldo Schemidt/AFP/Getty Images ( 519695431 )

The Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 14, 2013 spewing a cloud of ash and smoke. The National Disaster Prevention Centre (CENAPRED) raised the alert level on Sunday to "yellow phase three". Ronaldo Schemidt/AFP/Getty Images ( 519711417 )

The Popocatepetl volcano spews ash and steam as seen from Santiago Xalitzintla, Mexico, Sunday evening, May 12, 2013. Seismic activity has increased at the Popocatepetl volcano near Mexico City, leading authorities to alert towns in two central states and the capital. (AP Photo/Marco Ugarte) ( Mexico Volcano )

The Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, is seen from Santiago Xalitxintla, in Puebla, on May 14, 2013 spewing a cloud of ash and smoke. The National Disaster Prevention Centre (CENAPRED) raised the alert level on Sunday to "yellow phase three". Ronaldo Schemidt/AFP/Getty Images ( 519711040 )

Two women walk in San Nicolas de los Ranchos community near Popocatepetl volcano, in Puebla, Mexico, on May 12, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Jose Castañares/AFP/Getty Images ( 519676405 )

Two ambulances remain parked at the entrance to San Nicolas de los Ranchos community near Popocatepetl volcano, in Puebla, Mexico, on May 12, 2013. According to a report by the National Center of Prevention of Disasters (CENAPRED) the yellow alert phase three is still in force. Jose Castañares/AFP/Getty Images ( 519676554 )

Backdropped by Popocatepetl Volcano, Mexico's second highest peak just 55 km southeast of Mexico City, a man rides his bicycle in San Nicolas de los Ranchos, in the state of Puebla, on May 14, 2013. The National Disaster Prevention Centre (CENAPRED) raised the alert level on Sunday to "yellow phase three" as the Popocatepetl continues to spew ash and smoke. Ronaldo Schemidt/AFP/Getty Images ( 519711745 )