Popocatépetl volcano spews incandescent material on Tuesday. The second highest volcano in the Mexico increased its activity, and authorities raised the alert to the second-highest level.

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Popocatépetl volcano spews incandescent material on Tuesday. The second highest volcano in the Mexico increased its activity, and authorities raised the alert to the second-highest level. / Getty Images

Popocatépetl volcano just outside Mexico City has been erupting occasionally since 1994, but over the past week it has rumbled every day.

Scientists have recorded hundreds of explosions, and webcams trained on the volcano have shown it spewing incandescent material. From Mexico City, you can see a column of ash rising from the summit.

Smoke, ash and molten rock spew into the sky from Popocatépetl on Sunday, posing risks to aviation and communities below. Two Mexico City airports temporarily halted operations on Saturday due to falling ash.

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Smoke, ash and molten rock spew into the sky from Popocatépetl on Sunday, posing risks to aviation and communities below. Two Mexico City airports temporarily halted operations on Saturday due to falling ash. / AFP via Getty Images

Volcanic ash from the Popocatépetl volcano falls over Atlixco, Mexico, on Monday. Authorities are preparing for possible evacuation and telling people to stay out of a 7.5-mile radius around the peak.

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Volcanic ash from the Popocatépetl volcano falls over Atlixco, Mexico, on Monday. Authorities are preparing for possible evacuation and telling people to stay out of a 7.5-mile radius around the peak. / AP

Like Mount Vesuvius in Italy and Mount St. Helens in Washington state, Popocatépetl is a stratovolcano capable of catastrophic, explosive eruptions, the last of which came around the year 800.

A car is covered with ashes Tuesday from the Popocatépetl volcano in the village of Santiago Xalitzintla in Puebla state, Mexico.

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A car is covered with ashes Tuesday from the Popocatépetl volcano in the village of Santiago Xalitzintla in Puebla state, Mexico. / AFP via Getty Images

A couple wears hoods and masks Monday to protect themselves from the ashfall of the Popocatépetl volcano in Atlixco, Mexico.

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A couple wears hoods and masks Monday to protect themselves from the ashfall of the Popocatépetl volcano in Atlixco, Mexico. / AP

Scientists in Mexico say it's impossible to tell how long this new activity will last, or whether recent activity might lead to such a blast. But they say the 17,700-foot volcano, known locally as El Popo, will give enough warning to evacuate the millions who could be in danger.

Mexico has deployed about 7,000 troops to the region to help prepare for an evacuation if one is needed. More than 25 million people live within 60 miles of the peak.

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Mexican soldiers drive in Santiago Xalitzintla on Tuesday as ash from the Popocatépetl volcano blankets the streets.

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Mexican soldiers drive in Santiago Xalitzintla on Tuesday as ash from the Popocatépetl volcano blankets the streets. / AP

Mexican soldiers sweep ashes from the streets Tuesday in Santiago Xalitzintla.

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Mexican soldiers sweep ashes from the streets Tuesday in Santiago Xalitzintla. / AFP via Getty Images

Women walk on the ash-covered streets Monday in Santiago Xalitzintla.

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Women walk on the ash-covered streets Monday in Santiago Xalitzintla. / AP