An overcrowded bus veered off a road in northwest Nepal Tuesday and fell down a hill, leaving at least 30 dead and an additional 35 others injured, a government official said.

The bus was traveling from Nepal's capital of Kathmandu to the village of Chilime when it fell down the slope, reported the BBC. The official reason for the crash is still unknown, but it's believed that the bus being overcrowded was a leading factor.

The bus was overcrowded and people were reportedly riding on the roof due to a severe fuel shortage in the country that has limited transportation.

Nepalese military troops, police officers and locals carried out a rescue operation after the crash in Ramche, a village in Rasuwa about 20 miles north of Kathmandu, government administrator Shiv Ram Gelal said, according to CNN.

Most of the injured were taken to a hospital in Rasuwa, while several others were taken to a hospital in Kathmandu.

The fuel shortage has forced people to travel on the roofs of buses, which is usually forbidden due to safety concerns, reported The Associated Press. It has become a common sight to see bus roofs packed with passengers, and local authorities rarely stop them.

Nepal usually gets its fuel from India, but the import of fuel and other supplies has been cut off since September due to the blockage of a key border point between the two countries at the hands of ethnic protesters.

Police are investigating the incident.