Authorities said the bus, returning from a visit to Bolivia's famed Salar de Uyuni salt flats, overturned shortly before dawn yesterday.
The bus, which had set out from Uyuni, "stopped in Potosi and was headed to La Paz, carrying about 35 people mostly foreigners such as Egyptians, Italians and Brazilians," Oruro transit police officer Arturo Gutierrez told Radio Erbol.
Two Germans and a Chilean were among those seriously injured, he added.
San Juan de Dios Hospital in Oruro has said some people were treated and released, but did not immediately provide numbers or nationalities.