The accident occurred last night after the bus left the provincial capital of Santa Teresa. It fell about 650 feet (200 meters) into the chasm. Authorities said bodies were found as far as 100 metres away from the impact site.
Firefighter Captain David Taboada said no survivors were found. He also said authorities had not determined the cause of the accident.
The high-altitude roads of the Peruvian Andes are notorious for such bus plunges, with poor farmers comprising many of the victims.