The iconic white-capped volcano known as Popocatepetl, located less than a two-hour drive from Mexico City, awoke in April after more than a decade of silence.

Spurting lava and steam for kilometres, the volcano threatens to dump ash on the more than 25 million people that live within a 100km radius.

Scientists say they cannot predict when it will erupt, but the country's Natural Disaster Prevention Centre has increased its alert to the third highest level.

Al Jazeera's Rachel Levin reports from Puebla, Mexico.