"So far we are talking about 25 confirmed dead and 24 injured, but we are still working," Highway Patrol Chief Fernando RojasCommander Fernando Rojas told reporters.
According to the preliminary police report, the accident occurred around midnight on Sunday in the Amazon region of Los Yungas - near La Paz - where the bus went off the road after a triple collision.
Interior Minister Carlos Romero said the bus driver tried to pass a tanker truck, collided with another vehicle and then tumbled down a roughly 300-meter deep in the northern town of Yolosa, roughly 50 miles (80 kilometers) north of the capital, La Paz.
Road accidents are frequent in Bolivia and this year alone, more than a hundred people have been killed by vehicle collisions or landslides.
"We are very sad about the serious accident that took place on the La Paz-Yungas highway. Our deepest condolences to the relatives of the deceased, and to the brothers and sisters, we ask you to always be very careful, taking care of life is above all," President Evo Morales tweeted this week.