KATHMANDU, Nepal — An overcrowded bus slipped off a mountain road in Nepal on Tuesday, killing at least 14 people, an official said.

The bus was carrying passengers both inside and on the roof, said Dhading District Administration official Toran Parajuli. He said that the road was covered in parts by mud from landslides, and that the bus driver appeared to be trying to negotiate around these areas when the crash happened.

The bus slipped off the road near Lapang Phedi village, 120 kilometers (75 miles) west of Kathmandu, the capital, and rolled about 300 meters (980 feet) before stopping on the banks of the Ankhu River.

Parajuli said rescuers were at the crash site. At least nine people were injured, with a helicopter flown to the site from Kathmandu to try to fetch them.

The bus, which was on a local route and carrying all Nepali nationals, was unusually crowded because people in Nepal are heading to their village homes this week for the Hindu festival of Dashain, which begins Saturday. The two-week festival is the most important one in Nepal, a predominantly Hindu country.

It is illegal to travel on the roof of a bus in Nepal, but police do not monitor rural roads. Traffic accidents in the Himalayan country are blamed mainly on poorly maintained roads and vehicles.