NEW DELHI — At least 20 people have been killed after a passenger bus veered off a bridge and plunged into a river in the western Indian state of Rajasthan.

Government official K.L. Katara says another 10 passengers have been injured in the crash on Saturday in Sawai Madhopur district of Rajasthan state.

The bus reportedly broke through the bridge wall. It’s not immediately clear what caused the driver to lose control of the bus.

A rescue operation is underway.

Driver fatigue, negligence, poor quality roads and vehicle maintenance are the usual causes of such accidents in India. Police figures show India has the world’s highest road accident death toll, with more than 110,000 people dying each year in crashes.