At least 17 people were killed and 30 others injured after a passenger bus plunged off a cliff in the mountainous Cusco region of Peru on Tuesday, according to local police.

The bus carried 48 passengers while heading from the Amazon rainforest city of Puerto Maldonado to the highland city of Cusco, said police officer Alvaro Mendoza.

"The victims were found among twisted metal," Mendoza added. "It was difficult to get them out because of the heavy rain falling in an area of very rough terrain."

An investigation into the cause of the accident is underway.