An activity bulletin by geology institute Ingeominas said the volcanic activity continues in the Orange Level, suggesting probable eruption.
Nevado del Ruiz which lies 28km southeast of Manizales, most recently erupted at the end of June resulting in the evacuation of over 2,000 people from the area.
Thursday’s report said the activity over the preceding 12 hours recorded continuous volcanic tremors, while satellite images showed significant emissions of sulfur dioxide proving the volcano’s instability.
Nevado del Ruiz is Colombia’s most dangerous volcano with an eruptive history of 1.8 billion years. The eruptions usually take the form of pyroclastic flows resulting in mudslides, or lahars.
The most deadly lahar in history happened 1985 when a small eruption caused icecaps around the volcano to melt and rivers to rise, completely destroying one town and partially destroying three others, resulting in an estimated 25,000 deaths.
According to Ingeominas the “possibility of a lahar during a phase of some importance is very high — 100%.”
Emergency agencies asked people in the area to stay alert for announcements from meteorological centers because it is possible they will need to be evacuated in the case of increased volcanic activity.