Heavy rain and torrents of cold lava and mud flowing down a volcano’s slopes on Indonesia’s Sumatra island have triggered flash floods that killed at least 15 people and injured several others.

Monsoon rains and a major mudslide from a cold lava flow on Mount Marapi caused a river to breach its banks and tear through mountainside villages in Agam and Tanah Datar districts in West Sumatra province just before midnight on Saturday.

National Disaster Management Agency spokesman Abdul Muhari said the floods swept away people and submerged more than 100 houses and buildings.

Cold lava, also known as lahar, is a mixture of volcanic material and pebbles that flow down a volcano’s slopes in the rain.

By Sunday, rescuers had pulled out 11 bodies in the worst-hit village of Canduang and recovered four others in the neighbouring village of Sungai Pua, Mr Muhari said.

The agency said in a statement that at least seven villagers were injured by the flash floods, and rescuers were searching for other possible victims. It said 60 people had fled to temporary government shelters.

The disaster came just two months after heavy rain triggered flash floods and a landslide in West Sumatra’s Pesisir Selatan and Padang Pariaman districts, killing at least 21 people and leaving five others missing.

The 9,465ft Mount Marapi erupted late last year, killing 23 climbers who were caught by a surprise weekend eruption.

The volcano has stayed at the third highest of four alert levels since 2011, indicating above-normal volcanic activity under which climbers and villagers must stay more than 1.8 miles from the peak, according to Indonesia’s Centre for Volcanology and Geological Disaster Mitigation.

Marapi is known for sudden eruptions that are difficult to predict because the source is shallow and near the peak. Its eruptions are not caused by a deep movement of magma which sets off tremors that register on seismic monitors.