The accident occurred before dawn today as the bus traveled on a highway between Santo Domingo and Aloag, southwest of Quito.
The vehicle drove into a ravine and rolled as it fell some 300 meters, police said.
The bus had left the coastal city of Manta late yesterday and was destined for the capital.
The survivors were taken to local hospitals with multiple injuries, Christian Rivera of the Emergency Operations Committee told the El Comercio newspaper.