Cornelio Coaquira, the mayor of the nearby village of Velille, was among dozens of villagers who tried to rescue survivors after the crash.
"The bus is completely destroyed at the bottom of the ravine, and the worst of it is that we are isolated here like many towns in Peru, without the communication" that could have saved lives, The Associated Press news agency quoted Coaquira as saying.
Officials are still investigating the cause of the accident.
But Edison Olivares, a teacher in Velille, said the stretch of the highway where the accident took place is in bad condition with many potholes, the AP reported.
Road accidents occur frequently on Peru's mountain highways where many roads are in disrepair.