(CNN) -- Eighteen people were killed and 43 seriously injured after the bus they were traveling in plunged into a ravine in a mountainous area south of the Indonesian capital, authorities said.
The crash took place Wednesday morning in Puncak, West Java, said Sutopo Purwo Nugroho, a spokesman for the national disaster agency.
The passengers on the bus were members of different churches in Jakarta who were returning from a retreat. The cool, mountainous area of Puncak is a popular holiday destination for Jakarta residents.
Nugroho said there were indications that the driver lost control of the bus after its brakes stopped working. The bus then rammed into a parked truck and fell into the ravine, he said.
The injured are being treated in hospitals in the area.
The rugged area is prone to road accidents, and road safety is generally poor in most parts of Indonesia.