Eight people were found dead in Sukameriah village, near Mount Sinabung on the western island of Sumatra, four or whom were high school students on a sightseeing trip to the volcano, said Sutopo Purwo Nugroho, the spokesman for the National Disaster Management Agency.
Three other bodies were recovered from the village later in the afternoon and were taken to hospital for identification, Nugroho added.
Photographs taken by an AFP reporter at the scene showed apocalyptic scenes of corpses covered in ash just yards from a fallen motorcycle as masked rescuers wearing battled through the fumes to reach them.
"We suspect there are more victims but we cannot recover them because the victims are in the path of the hot (ash) clouds," Nugroho said.
Three other people, a father and his son as well as another man, suffered from burn injuries, Karo district official, Johnson Tarigan, told AFP.
He said the three were in an intensive care unit of a local hospital.
Mount Sinabung had shown a reduction of activity since mid-January.
