Officials were forced to extend the danger zone and evacuate hundreds of thousands of people on the island of Java.
Blasts from Merapi have killed at least 44 people, including six who died in a burst of hot volcanic debris on Wednesday.
Residents who had failed to evacuate, or had returned home, fled in panic as lava and burning rocks burst from Merapi’s crater.
Officials believe that some of the new fatalities were due to villagers believing their homes and fields were far enough away from Merapi's slopes to be safe from the pyroclastic flows of super-heated debris that killed others.
Vulcanologists warned that Mount Merapi could continue to erupt for weeks or even months.
Several other volcanos in the Indonesian archipelago, including Mount Anak Krakatau volcano (Child of Krakatoa), have begun to show signs of increased activity over the past three weeks.
Photo: Rudi Yanto - Flickr