After the eruption of Mount Marapi volcano, bodies of 11 climbers were recovered, while the search is on for the missing 12.
Since 2011, Marapai has stayed at the third highest of four alert levels. The third level indicates above normal volcanic activity and prohibiting climbers or villagers within three kilometres of the peak.
Hendra Gunawan, the head of the Centre for Volcanology and Geological Disaster Mitigation, said that no climbing is allowed to the peak at this stage.
Climbers were only allowed below the danger zone, but sometimes they hike further and break the rules, said Gunawan.
About 75 climbers had started their way up the nearly 2,900-metre mountain on Saturday . Among them, eight were rescued and rushed to hospitals with burns and minor injures, said Hari Agustian, an official at the local Search and Rescue Agency in Padang, the West Sumatra provincial capital.
Marapi spewed thick columns of ash as high as 3,000 metres in Sunday's eruption and hot ash clouds spread several miles. Volcanic debris engulfed nearby villages and towns.
The nearest villages include Rubai and Gobah Cumantiang. Around 1,500 people live in these villages.
Marapi has been observed regularly erupting since 2004 with a gap of 2 to 4 years, Gunawan said.
According to Gunawan, Marapi eruptions are always sudden and difficult to detect. West Sumatra's Search and Rescue Agency head Abdul Malik said rescuers found 11 bodies of climbers as they searched for those who still missing and rescued three others Monday morning.
Marapi is one among the 120 active volcanoes in Indonesia.