The accident occurred on a notorious bend of the Panamericana Norte highway known as “the curve of the devil,” around 45 miles north of Lima.
It was not clear exactly how many people were on the bus, which was traveling from the city of Huacho to Lima, and the search had been called off for the day, police said.
Another six people were found injured, with five people airlifted to a hospital in the nearby city of Callao.
Survivors said there were about 55 passengers on the bus.
The news agency Agencia Andina posted pictures of the crash site on Twitter, showing a bus upside down, its top half crushed, on the rocks below the cliff.
It is believed the accident happened when a truck traveling in the opposite direction suffered a mechanical failure and collided with the bus.
“It is very painful for us as a country to suffer an accident of this magnitude,” President Pedro Pablo Kuczynski said, expressing his condolences to the families of the victims.
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