At least eleven people were killed and dozens more were injured when a bus carrying high school students on a graduation trip crashed on Indonesia’s biggest island, police said Sunday.

The bus was carrying more than 60 students and teachers from the Java island town of Depok to Lembang, a popular tourist spot, when it crashed at 6:48 pm (1148 GMT) on Saturday.

The students had just celebrated their graduation and were on a school trip when the bus suddenly lost control and tilted to the left, crashing into a car and three motorbikes, West Java province police spokesman Jules Abraham Abast told AFP Sunday.

“Out of the passengers who died, nine of them were students, and one of them was a teacher,” Abast said.

The accident also killed one motorcyclist, seriously injured 13 people and caused minor injuries to 40 others, he added.

Local traffic police chief Undang Syarif Hidayat told broadcaster Kompas he suspected the bus’ brake malfunctioned before the crash, but Abast said police are still investigating the cause of the accident.

Deadly traffic accidents are common in Indonesia, where vehicles are often old or poorly maintained, and road rules are routinely ignored.

Last month, at least 12 people were killed when a car crashed into a bus and another car on a busy highway in West Java, as people travelled to celebrate Eid-al-Fitr with relatives at the end of the Islamic holy month of Ramadan.