Smaller eruptions have followed daily, interrupting flights and adversely affecting agriculture and wildlife. On May 29, some 600,000 salmon threatened by the ash were shipped out from a fish farm near the volcano.

Now experts warn that another, bigger explosion is possible.

“The most complex current eruptive scenario deals with an explosion associated with dome removal,” says Luis Lara, of the Volcano Hazards Programme at the Chilean geological survey.

The dome – a cone-shaped “roof” that is formed by accumulating layers of lava – is growing, and the potential for an explosion is real, Lara says.

Iván Alejandro Petrinovic, a geologist at the Universidad Nacional de Salta and the Argentinian national science council, agrees that there is a chance of a major explosion caused by the increase of magma pressure inside the volcano.

Although authorities say the falling ashes are not toxic, a “sanitary alert” was issued in the Argentine town of Esquel, and clean drinking water has been distributed.