Mount Gamalama on the Indonesian island of Ternate spewed more ash into the skies on Tuesday (December 6).
The debris travelled up to 500 metres into the air.
Volcanologists monitoring Gamalama's activity say conditions are fluctuating. The alert level is at the second highest.
The Sultan Babullah airport in the provincial capital has been closed since Monday (December 5).
Thousands living at the base of the volcano have fled their homes, taking shelter at a former government office building.
Indonesia lies on the Pacific 'Ring of Fire' and is prone to natural disasters like volcano eruptions, earthquakes, floods and tsunamis.