Officials in southern Colombia have issued a code orange alert for the newly-active Galeras volcano which they said could erupt in a matter of days or weeks, according to the state-run Geological and Mining Institute.
Authorities said they are continuing to monitor the nearby Huila volcano, also on orange alert, where sizeable volcanic activity also has been detected in recent weeks.
The Galeras volcano situated near the southern border with Ecuador is Colombia's most active volcano, with five eruptions over the past two years. It began rumbling back to life on October 27, officials said.
Some 7,000 people live in the vicinity of the volcano, which rises in the Andes mountain chain to an altitude of 4,270 meters (14,029 feet).
A 1993 eruption of Galeras killed nine people, including six scientists who had descended its crater to take gas samples.
Huila, at some 5,363 meters (17,595 feet), last erupted in November 2008, killing 10 people.