Police say at least 16 students were killed and another 32 injured when their bus fell into a ravine north of Bolivia's capital, La Paz.
Transit police chief Victorino Torres says the number of dead could increase because rescuers were still looking through the wreckage in the municipality of Acero Marka.
Torres told Red Uno television network Thursday that the students were between 16 and 18 years old, and were traveling to La Paz to participate in an inter-school sporting event.
He said the bus plunged into a 400-foot (120-meter) ravine.
Torres did not give the cause of the accident, but survivors said the driver tried to let another bus pass on the narrow road and went into the ravine.
Hospital official Fernando Arispe said some of the 32 injured were in "very serious" condition.