La Nacion reported Pablo Wagner, undersecretary for mining, characterized the eruption of the el Cordon del Caulle volcano in the Lago Ranco province as "moderate."
He said the wind direction had sent ash falling over populated areas of the country and water sampling would be conducted Sunday to check on sulfur levels.
"Do not panic," Mines and Energy Minister Laurence Golborne urged the Chilean public, adding there "ought not be an imminent danger" as long as people follow authorities' directions.
Voice of America, which noted it was the first time the volcano, located about 600 miles south of Santiago, had shown signs of life in a half century, sent a column of smoke and gas 6 miles into the air.
Authorities closed a border crossing into Argentina because of the danger presented by the volcano, VOA said.
The British newspaper The Guardian reported emergency officials said there were many small earthquakes in the region but no reports of any injuries. The country has about 2,000 volcanoes, of which about 500 are active.
The Guardian said the ash was blowing toward Argentina, forcing the closure of the airport in Argentine city of San Carlos de Bariloche.
Juli Kessler told the BBC she saw "big black clouds hanging over the Andes" mountains and ash dust on the road.