No evacuations have been ordered, but officials are urging people living near the Popocatepetl volcano, southeast of Mexico City, to gather important papers and have their escape routes planned.
A roiling white cloud of ash, gas, water vapor and superheated rock spewed high above the village of Xalitzintla, with the ash blowing toward the city of Puebla.
This week, authorities raised the alert level due to increasing activity at the volcano, which had its most violent eruption in 1,200 years in 2000.
Gregorio Fuentes Casquera, the assistant mayor of Xalitzintla, a village of 2,600 people about seven miles from the summit, said the town had prepared 50 buses and was sending out police teams to alert people to be ready to evacuate.
Casquera said he believed about half the populace would be willing to evacuate, while the rest would want to stay.
The Associated Press contributed to this report.