Mexico's Popocatepetl volcano erupts

Ash and smoke spewed from Popocatepetl Volcano as seen from San Buenaventura, in the Mexican central state of Puebla, on April 21, 2012.

Popocatepetl volcano spews lava, ash and steam during an eruption as seen from from Xalitzintla, Mexico, Saturday, April 21, 2012.

Residents of Santiago Xalitxintla, in the Mexican central state of Puebla, carry an image of "Senor de Las Misericordias" during a procession on April 21, 2012 while the nearby Popocatepetl volcano continues spewing ash and smoke.

A woman carries her baby at Zocalo Square in Santiago Xalitxintla, in the Mexican state of Puebla, April 21, 2012, while the nearby Popocatepetl volcano continues spewing ash and smoke.

A plume of ash and steam rise from the Popocatepetl volcano overshadowing the Catholic church Nuestra Senora de los Remedios (or Our Lady of Remedies), in Cholula, in the Mexican state of Puebla, Sunday, April 22, 2012.

Street lights illuminate the Mexican town of Xalitzintla as the looming Popocatepetl volcano spews lava, ash and steam in the town's shadows during an eruption, early Saturday, April 21, 2012.

Incandescent materials, ash and smoke are spewed from the Popocatepetl Volcano as seen from the Santiago Xalitxintla, in the Mexican central state of Puebla on April 20, 2012. Mexico's Popocatepetl volcano, outside the capital, rumbled continuously and spewed gases and glowing rocks to almost one mile beyond its crater, authorities said.

A plume of ash and smoke rises from the Popocatepetl volcano seen from the outskirts of the town of Santiago Xalizintla, Mexico, Friday, April 20, 2012. Authorities prepared evacuation routes, ambulances and shelters in the event of a bigger explosion after the volcano that looms over Mexico City emitted a low-pitched roar early Friday morning and spewed ash and steam.

Incandescent materials, ash and smoke are spewed from the Popocatepetl Volcano as seen from the Santiago Xalitxintla, in the Mexican central state of Puebla on April 20, 2012. Mexico's Popocatepetl volcano, outside the capital, rumbled continuously and spewed gases and glowing rocks to almost one mile beyond its crater, authorities said.

Incandescent materials, ash and smoke are spewed from the Popocatepetl Volcano as seen from the Santiago Xalitxintla, in the Mexican central state of Puebla on April 20, 2012. Mexico's Popocatepetl volcano, outside the capital, rumbled continuously and spewed gases and glowing rocks to almost a mile beyond its crater, authorities said.

In this April 18, 2012 photo, birds fly in the foreground as a plume of ash and steam rises from Popocatepetl volcano as seen from San Andres Cholula, Mexico. The volcano continues to shoot ash into the sky southeast of Mexico's capital, and television images on on April 20, show a reddish glow near the crater.

A plume of ash and steam rises from Popocatepetl volcano as seen from San Nicolas on April 20, 2012. Mexico's Popocatepetl volcano is continuing to spout gases and hot rock fragments, and it is dusting towns on its flanks with volcanic ash.

A plume of steam rises from the Popocatepetl volcano seen from the city of Puebla, Mexico, on April 14, 2012. An early morning exhalation from the volcano sent ashes to towns near the area as moderate activity at the volcano continues.

Families wait in a line for bottled water and face masks for protection from the ash spewed from the nearby Popocatepetl volcano in Xalitzintla, Mexico on April 20, 2012. A roiling white cloud of ash, gas, water vapor and superheated rock spewed from the cone of Popocatepetl high above the village of Xalitzintla, whose residents said they were awakened by a window-rattling series of eruptions.

A woman leaves a makeshift distribution center with bottled water and face masks for protection from the ash spewed from the nearby Popocatepetl volcano in Xalitzintla, Mexico on April 20, 2012.

A plume of ash and steam rises from the Popocatepetl volcano as seen from Huejotzingo, Mexico on April 20, 2012. Authorities this week raised the alert level due to increasing activity at the volcano, whose most violent eruption in 1,200 years occurred on Dec. 18, 2000.

A plume of ash and steam rise from Popocatepetl volcano seen from San Andres Cholula, Mexico on April 18, 2012. Mexico's Popocatepetl volcano is continuing to spout gases and hot rock fragments and it is dusting towns on its flanks with volcanic ash.

A plume of ash and steam rises from the Popocatepetl volcano as seen from Huejotzingo, Mexico on April 20, 2012. Authorities this week raised the alert level due to increasing activity at the volcano, whose most violent eruption in 1,200 years occurred on Dec. 18, 2000.

A plume of ash and steam rises from Popocatepetl volcano as seen from San Nicolas, Mexico, on April 20, 2012. Mexico's Popocatepetl volcano is continuing to spout gases and hot rock fragments and it is dusting towns on its flanks with volcanic ash.

Residents stand next to an evacuation route sign in the village of Xalitzintla, Mexico, on April 20, 2012. A roiling white cloud of ash, gas, water vapor and superheated rock spewed from the cone of Popocatepetl high above the village, whose residents said they were awakened by a window-rattling series of eruptions.

A woman leaves a makeshift distribution center with bottled water and face masks for protection from the ash spewed from the nearby Popocatepetl volcano in Xalitzintla, Mexico, on April 20, 2012. A roiling white cloud of ash, gas, water vapor and superheated rock spewed from the cone of Popocatepetl high above the village of Xalitzintla, whose residents said they were awakened by a window-rattling series of eruptions.

Ash and smoke are spewed from Popocatepetl Volcano as seen from the town of Xalitxintla in the central state of Puebla, 12 kilometers from the crater, on April 17, 2012. Residents of nearby communities reported roaring noises from the Popocatepetl volcano near Mexico City on Tuesday after signs of increased activity prompted authorities to raise alert levels.