Ash is raining down from the so-called "Volcano of Fire" in western Mexico and people living in its shadow are being relocated after it spectacularly erupted.
The interior ministry said the volcano in Colima state could continue to spew lava before waning in a few weeks - or possibly experience its biggest eruption in more than a century.
More than 80 people left nearby communities after the volcano sent a four-kilometre column of ash skyward late on Friday (local time).
Ash and lava continued to flow out the crater on Saturday.
One village at the foot of the mountain, Yerbabuena, was smothered in up to five centimetres of ash, authorities said, and rain also tumbled down, adding to the misery.
Ash travelled as far as the city of Colima, where residents wore masks as a thin layer of talc-like material covered streets and cars.
"This is the strongest activity since 2005," civil protection official Luis Felipe Puente told local radio.
The interior ministry said the volcanic activity was "atypical, presenting conditions similar to those of 1913," when a major eruption took place and covered the region in ash.
The ministry said three scenarios are possible: A gradual waning of activity in coming weeks, a 1913-like explosion or a collapse of the volcano's dome.