An overcrowded passenger bus has skidded off a cliff in Sri Lanka, killing 21 people and injuring at least 24 others.

The accident – among the deadliest recorded in Sri Lanka for decades – occurred in the early hours of Sunday in a mountainous area near the town of Kotmale, about 86 miles east of the capital Colombo.

The state-owned bus was carrying around 70 passengers – about 20 more than its capacity – when the driver lost control and it veered off the road before dawn, police said.

‘We are trying to establish whether it was a mechanical failure or if the driver fell asleep at the wheel,’ a local police official said, speaking on condition of anonymity.

Deputy Transport Minister Prasanna Gunasena explained at the scene that the injured were rushed to two area hospitals. Reports have claimed the bus was carrying dozens of Buddhist pilgrims.

‘Twenty one have died and we are trying to identify the victims,’ Gunasena added.

The toll could have been higher, the minister said, if not for local residents helping pull the injured from the mangled wreckage and rushing them to hospital.

Images of the disaster showed the bus lying overturned at the bottom of a precipice while workers and others helped remove injured people from the rubble.