The search and rescue agency said in a statement on Thursday that the bus driver lost control shortly before the accident in an area near the city of Sumedang in the province of West Java.
The ministry said the bus was carrying high school students and some parents. There were 39 survivors.
Crime scene photos showed that the bus ended up on its side, with rescuers looking for more victims.
Supriono, an official with the local search and rescue agency, said later that the evacuation efforts were completed and the survivors were taken to a nearby hospital.
The exact cause of the accident was not immediately clarified, although the ministry said there were initial indications that the vehicle’s assessment tests were not up to date.