Authorities in Colombia's south western departments Huila and Cauca are on alert after the Nevado del Huila volcano spewed ashes on Friday.
Following the activity, the nearby river Paez was reported to change color and a intense smell of sulfur occured in the area where ash came down.
Authorities warn locals not to drink from the rivers as the eruption may have contaminated the water.
Hospitals in the region are prepared for victims if the volcano comes to a violent eruption.
The volcano showed seismic activity a week ago already.
