Torrential rain on Saturday evening caused flash floods, landslides, and cold lava flow, which is a mixture of volcanic ash, rock debris and water that flows like mud, in three districts in West Sumatra province, Abdul Malik, the chief of the provincial rescue team told Reuters.
The cold lava flow, known in Indonesia as a lahar, came from Mount Marapi, one of Sumatra's most active volcanoes.
In December, more than 20 people were killed after Marapi erupted. A series of eruptions followed afterwards.
"The heavy rain swept materials such as ash and large rocks from the Marapi volcano," said Abdul Malik.
"Cold lava flow and flash floods have always been threats to us recently. But the problem is, it always happens late at night until dawn," he added.
Abdul said around 400 personnel, consisting of local rescuers, police, and military have been deployed to search for the missing people on Monday, helped by at least eight excavators and drones.
The rescue efforts that began on Sunday have been complicated by damaged roads, making it difficult for rescuers to pass through.
The national disaster and management agency BNPB said in a statement almost 200 houses were damaged and 72 hectares (178 acres) of lands, including rice fields, were affected. At least 159 people from Agam district have been evacuated to nearby school buildings, the BNPB said.
Footage shared by the BNPB showed the roads and rice fields were covered by mud. The floods also brought logs and large rocks into settlements.
Eko Widodo, a 43-year-old survivor, recalled the floods came instantly.
"The flooding was sudden and the river became blocked which resulted in the flow of water everywhere and it was out of control."