ROME — At least 38 people died and more than 10 were seriously injured on Sunday night when a bus plunged off a viaduct on a treacherous stretch of mountainous highway in the Campania region of southern Italy, officials told the Italian news media.

The highway police told state radio that the bus slammed into cars that had slowed because of heavy traffic about 160 miles south of Rome. The bus then fell 100 feet down a ravine. Italian television showed images of rescue workers pulling people from dozens of mangled cars.

Many of the bus’s passengers were from one vacationing family. Italian news media showed a row of corpses under white sheets in the early morning light on Monday.

Crews moved the bus to a demolition center for investigation. It crashed along a curving descent on the A16 highway between Monteforte Irpino and Baiano, near Avellino.