Indonesian officials have issued a red alert, warning that the nation’s most active volcano could be about to erupt.
Officials have ordered thousands of people to evacuate a 10-kilometre ring around Mount Merapi in central Java.
They say earthquakes over the past week have pushed up molten rock, which is now just a kilometre below the crater.
Emergency shelters are being prepared for an influx of evacuees.
But many of those in the evacuation zone are concerned about leaving livestock and crops unattended and they have been reluctant to move.
Two people were killed when Merapi last erupted in 2006.
But the worst death toll was in 1930 when 1,300 people died.
A government vulcanologist says he doubts this possible eruption would be that powerful.