Dozens killed in 'cold lava' mudslides and flash floods in Indonesia

Drone pictures show damage to flood-affected areas, including submerged houses and cars stuck on flooded roads.

A torrent of "cold lava" and mudslides have killed at least 41 people on Indonesia's Sumatra Island.

A further 17 people are missing after heavy rains and flash floods caused a river to breach its banks, triggering a deluge of cold lava to flow from Mount Merapi.

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

The mudslides tore through mountainside villages along four West Sumatra districts just before midnight on Saturday, submerging nearly 200 buildings and houses.

People inspect buildings damaged by a flash flood in Agam, West Sumatra Credit: AP

Rescuers on Monday recovered more bodies, although authorities struggled to get tractors and other heavy equipment to the areas.

Videos released by the National Search and Rescue Agency showed roads transformed into murky brown rivers, and villages covered by thick mud and uprooted trees.

"The devastated area is so vast and complicated, we badly need more excavators and mud pumps," said Abdul Malik, who heads the search and rescue office in Padang, the provincial capital.

Rescue teams cross the fast-moving river while searching for victims.

Bodies have mostly been recovered from the worst hit villages in Agam and Tanah Datar districts, according to Ilham Wahab, who heads the West Sumatra Disaster Mitigation Agency.

"Bad weather, damaged roads, and access that is blocked by thick mud and debris are hampering relief efforts," Wahab said.

The flash floods also caused main roads around the Anai Valley Waterfall area in Tanah Datar to be blocked by mud, cutting off access to cities, police said.

People examine the damage at an area badly affected by flash flooding Credit: AP

The disaster comes just two months after heavy rains triggered a landslide in West Sumatra, killing at least 26 people and leaving 11 others missing.

An unexpected eruption of Mount Marapi in December last year killed 23 climbers.

Separately, the Mount Ibu volcano erupted on Monday in Indonesia's North Maluku province, spewing grey ash and dark clouds 5,000 metres into the sky for five minutes, officials said.

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