The ash from the Tungurahua volcano, which will likely lead to heavy crop loss, could also cause health problems, officials said.
But most residents of the provincial capital Ambato, in Ecuador's central Andean valley, ignored government recommendations to wear masks, health officials said.
"People have to protect your nose and eyes, because the volcanic dust causes problems in the respiratory system," provincial health Director Maria de Lourdes Freire told Quito's El Comercio newspaper.
No ash-related illnesses were reported.
Residents and city workers swept blankets of ash from the streets, the newspaper said.
"Since the reactivation of the volcano this year, this is the first time that the dust has fallen on the streets of the city," city worker Luis Miniguano told the newspaper.
The volcano, whose name means "Throat of Fire," is located about 112 miles south of Quito.
It spewed ash columns as high as 2 1/2 miles more than 20 times Wednesday after a massive eruption Jan. 11, Daniel Andrade of the country's Institute of Geophysics told the newspaper.