Story highlights People were on the roof of the bus when it crashed, a police officer says

The vehicle tilted over and plunged 650 feet down a hill, he adds

(CNN) An overcrowded bus skidded off a road Tuesday in Nepal and plunged down a hill, killing at least 30 people and injuring 35 more, a government official said.

People were riding on the roof of the packed bus when it tilted over -- apparently because of the excess number of passengers -- on a gravel road, said Shiva Ram Gelal, chief district government officer in Nepal's Rasuwa district. The vehicle then slid about 650 feet (200 meters) down a hill.

Nepalese military troops, police officers and locals carried out a rescue operation after the crash in Ramche, a village in Rasuwa about 20 miles (32 kilometers) north of Kathmandu, according to Gelal.

Most of the injured have been taken a hospital in Rasuwa, while a few have been taken to a hospital in the Nepalese capital.

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A fuel shortage in Nepal has hit public transportation hard, leading to fewer vehicles in service. As a result, those that are running are more likely to carry more riders than they should, the government official said.