Heavy rains and torrents of cold lava and mud flowing down a volcano's slopes on Indonesia's Sumatra island triggered flash floods that killed at least 37 people and more than a dozen others were missing, officials said Sunday.

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 four districts in West Sumatra province just before midnight on Saturday. The floods swept away people and submerged more than 100 houses and buildings, National Disaster Management Agency spokesperson Abdul Muhari said.

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 afternoon, rescuers had pulled out 19 bodies in the worst-hit village of Canduang in Agam district and recovered nine other bodies in the neighboring district of Tanah Datar, the National Search and Rescue Agency said in a statement.

The agency said that eight bodies were pulled from mud during deadly flash floods that also hit Padang Pariaman, and one body was found in the city of Padang Panjang. It said rescuers are searching for 18 people who are reportedly missing.

Flash floods on Saturday night also caused main roads around the Anai Valley Waterfall area in Tanah Datar district to be blocked by mud, cutting off access to other cities, Padang Panjang Police Chief Kartyana Putra said Sunday.

Videos released by the National Search and Rescue Agency showed roads that were transformed into murky brown rivers.

The disaster came just two months after heavy rains 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 2,885-meter (9,465-foot) 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 3 kilometers (about 2 miles) from the peak, according to Indonesia's Center 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, and its eruptions aren't caused by a deep movement of magma, which sets off tremors that register on seismic monitors.

Marapi has been active since an eruption in January 2023 that caused no casualties. It is among more than 120 active volcanoes in Indonesia. The country is prone to seismic upheaval because of its location on the Pacific "Ring of Fire," an arc of volcanoes and fault lines encircling the Pacific Basin.