Authorities raised an alert level to "yellow," indicating elevated volcanic activity, and established a no-entry perimeter five kilometers (three miles) around the crater.
They also alerted aircraft to the drifting plume.
Authorities stayed in close contact with officials in Talabre, a town 30 kilometers from the volcano, in case evacuations were required. But no property damage was reported.
Lascar, with an elevation of 5,592 meters above sea level, is 70 kilometers from San Pedro de Atacama, a popular tourist center that draws visitors for trekking, amateur astronomy and visits to the Atacama Desert, the driest place on Earth.
Lascar erupted in 1993 but also had lesser volcanic activity in 2006 and 2015.
Farther to the south, yellow alerts remain in effect for regions around the Nevados de Chillan volcanic complex and the Villarrica volcano.