The Popocatepetl volcano near Mexico City shook with increasingly powerful explosions that have forced the Mexican government to evacuate some residents and launch emergency measures.

While the volcano has been in almost constant activity for the last 19 years, emitting a small eruption of ash almost daily, the new activity has blown glowing rocks over the edge of the crater. A half-mile tower of steam is shooting into the sky.

The government has deployed military and federal police to the region to create a seven-square-mile zone of exclusion around the volcano. Local authorities are preparing shelters for people being forced to evacuate if the activity of the volcano increases beyond current levels.