A packed tourist bus returning from an outing collided with a motorbike and plunged from a hill on Indonesia’s main island of Java after its brakes apparently malfunctioned, killing at least 27 people, police said on Sunday.

At least 18 others were hospitalised with injuries, some in critical condition, following the crash Saturday on a winding slope in Subang in West Java province, said local police chief Muhammad Joni.

Television footage showed police, soldiers and medical personnel evacuating the victims from the upside-down bus, which was carrying more than 40 local tourists. The bus was headed for Tangerang, a satellite city just south of the capital, Jakarta, from West Java’s Tangkuban Perahu, a popular mountainous resort.

Joni said police were still investigating the cause of the accident, but a preliminary investigation showed the brakes malfunctioned while the bus was going up the hill and rolled down, hitting a motorbike before falling into a grass field.