The search and rescue agency said in a statement on Thursday that the driver of the bus 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 transporting high school students and some parents. There were 39 survivors.
Photos of the scene showed the bus landing on its side with rescue workers searching for more victims.
Supriono, a local search and rescue agency official, later said evacuation efforts had been completed and survivors taken to a nearby hospital.
The exact cause of the crash was not immediately clear, although the ministry said there were initial indications that the vehicle’s roadworthiness tests were not up to date.