The driver missed a difficult turn around 9:15 a.m. and the vehicle toppled to the bottom of a ravine, NepalNews.com reported.
The report said it's common for vehicles to be overloaded in rural areas.
Police said seven passengers were declared dead at the scene, while the other four died of their injuries in two hospitals in the district of Kaski, the Himalayan Times reported.
Hours after the crash, only nine of the victims had been identified, the reports said.
Emergency and rescue workers in Kaski were already exhausted from a day earlier when a flash flood on the Seti River killed 15 people and washed away bridges and homes, NepalNews.com said.