Ashes from the Tunguarahua volcano are rising 2 1/2 miles into the sky, damaging crops and endangering residents in the area.
Authorities in Ecuador urged people to cover their mouths and noses and to shut windows. Schools in the area were suspended until at least Thursday.
Tunguarahua has been active since 1999 and its eruptions killed at least four people in 2006.
The volcano is 85 miles south of Quito, Ecuador's capital.
The Associated Press contributed to this story.