LA PAZ, July 31 (Xinhua) -- At least four people died on Sunday after a bus fell into a ravine in Ilipana community in the western Bolivian department of La Paz, local authorities reported.

Police said 20 others were injured in the accident. They have been taken to health centers in nearby towns and hospitals in the city of La Paz.

Edgar Toro, a journalist from the town of Apolo, told Xinhua that the accident occurred early on Sunday morning near the municipality of Apolo, north of La Paz.

A passenger who survived, named Saul Arbiri, told local media that most of the passengers were from the community of Suyo Suyo, and the driver had fallen asleep when the bus veered off the road and fell into the ravine.

Local authorities have yet to detail the cause of the accident.