At least 11 of those who died in the flooding Friday were students, according to Sutopo Purwo Nugroho of the disaster mitigation agency. Some students are still missing. The flooding was in Mandailing Natal, North Sumatra.
Some of the students were buried under debris and mud after the Aek Saladi river overflowed, according to state media.
Indonesia has been hit by a series of natural disasters in recent weeks, including a powerful earthquake that hit the island of Sulawesi on September 28. In the towns of Baleroa and Petobo, rivers of soil swept away entire neighborhoods in the aftermath of the 7.5-magnitude earthquake and ensuing tsunami.
The death toll from the quake is nearly 2,000.