Mexico's Popocatepetl volcano releases gas into the atmosphere, as Mexican authorities raise the alert level.

The new warning indicates possible magma expulsion and explosions of increasing intensity.

But for residents of the small town of San Pedro Benito Juarez, this is nothing new.

Popocatepetl is one of the world's most active volcanoes, and one public security official said those who live nearby are aware of what to do in an emergency.

(SOUNDBITE) (Spanish) MINISTER FOR PUBLIC SECURITY IN PUEBLA STATE, ARDELIO VARGAS:

"So far we have not reached a critical phase of emergency, which is characterised precisely by an evacuation. So the residents are very clear on what to do in case of an emergency. They know how to use their vehicles in the result of an evacuation and where they can go to receive adequate attention."

The volcano has spewed smoke and ash sporadically over the last few years.

A major eruption in 2000 forced the evacuation of nearly 50,000 residents.

Simon Hanna, Reuters.