Landslides have killed at least three people at a Chinese-backed power plant on North Sumatra, the disaster agency said Friday, with fears that the toll would rise.
Heavy rains pounded the area in North Sumatra on Thursday evening, triggering the deadly torrent.
"There are three people dead," the National Disaster Mitigation Agency (BNPB) spokesman Raditya Jati told AFP. "The rescue team is still searching for other victims," he added, without specifying a figure.
A local disaster official said at least nine people were missing and feared buried beneath a mountain of mud and debris, including a Chinese employee of the Batang Toru hydropower facility.
Fatal landslides and flash floods are common across the country during the rainy season.
This month, more than 200 people were killed in a cluster of far-eastern islands and neighbouring Timor Leste as Tropical Cyclone Seroja turned small communities into wastelands of mud and uprooted trees.
Seroja, one of the most destructive storms to hit the region in years, forced thousands to flee to shelters.
BNPB has estimated that 125 million Indonesians – nearly half of the country's population – live in areas at risk of landslides.
The disasters are often caused by deforestation and poor mitigation planning, according to environmentalists.