Search and rescue said in a statement on Thursday that the driver of the bus lost control shortly before the crash in an area near Sumedang city, West Java province.
The ministry said the bus was transporting high school students and some parents. There were 39 survivors.
Photos of the scene showed that the bus had ended up on its side with rescuers looking for more victims.
Supriono, a local search and rescue officer, later said the evacuation efforts had been completed and the survivors had been transferred 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 drivability tests were not up to date.