LIMA, Peru -?Authorities say 21 people were killed and 38 seriously injured when a bus veered off the road and plunged into a ravine in Peru's southeastern Andes Mountains.

It is the second deadly road accident in Peru in a week. Last Monday, 38 people died and 84 were injured when three buses and a truck collided on the South American country's main coastal highway.

The latest accident took place on Monday in Ayacucho province. The bus fell into a 1,000-meter (3,280-foot) deep ravine, Col. Orfiles Bravo told local media.

He said the cause of the accident was still not known. He said the bus was reduced to "a mass of twisted metal.''