Sutopo Purwo Nugroho, a spokesman for the country's disaster relief agency, told CNN all the known dead were in the village of Sukameriah near Mount Sinabung.
They were killed by hot ash.
Sinabung in North Sumatra is one of four active volcanoes in Indonesia. The volcano erupted in 2010 after four centuries of inactivity and then began spewing ash and lava again in late 2013.
About 33,000 people had moved out of the area since September because of the eruption, Sky News reported.
Two of the dead had come to Sukameriah to visit the graves of relatives, and a man who returned to the village to check on his house was injured.
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