A passenger bus in Sri Lanka’s central hill country skidded off a cliff near Kotmale early Sunday, killing 21 people and injuring 35 others, according to police.

The bus, carrying around 50 passengers, was operated by a state-run company.

Authorities are investigating whether driver error or a mechanical fault caused the crash, NBC News has reported.

Deadly bus accidents are common in the region due to reckless driving and hazardous road conditions.

Written by B.C. Begley