The disaster occurred yesterday as more than 70 students were visiting the Air Terjun Dua Warna waterfall in North Sumatra province.
Darwin Surbakti, an official from the local Disaster Management Agency, today said that 21 students were reported missing after the disaster.
He said the bodies of five men and a woman were found today around 3 kilometers (2 miles) downstream from the waterfall.
About 150 rescuers, including soldiers, policemen and volunteers, are searching for the 15 still missing. Seasonal rains often cause flooding and landslides in Indonesia, a chain of 17,000 islands where millions of people live in mountainous areas.