Thirty-eight people were killed and at least 18 injured when a bus plunged 25 metres off a viaduct in Italy, in the second major transport disaster in southern Europe in less than a week.

Initial reports suggested that the coach was travelling at high speed and hit four or five cars before crashing over the roadside barriers on a stretch of road near Monteforte Irpino, east of Naples, on Sunday night.

There were around 50 people on board, many of them children.

It was one of Italy’s worst road accidents and came just five days after 79 people were killed when a high-speed train derailed in the Spanish pilgrimage town of Santiago de Compostela.

Prime Minister Enrico Letta, on an official trip to Athens, cancelled a private visit to the Acropolis.

“It is a very sad day for Italy, what happened last night. There are no words for it,” he told reporters. “It is a huge tragedy.”

Italy’s government has declared today as a day of national mourning, when the funeral of the victims will take place. Pope Francis said in a telegram he shared the pain the Campania region was suffering and he prayed for the victims and for the injured to recover quickly.

A statement from motorway operator Autostrade per l’Italia said the coach appeared to have been travelling fast near slower-moving traffic, even though a lower speed limit had been clearly indicated.

Officials were examining onboard instruments and the guardrail on the highway where the accident occurred to try to determine the cause of the crash.

“You would think that the barriers on the viaducts and bridges should prevent this type of accident but evidently it seems the impact was so strong that even the barrier gave way,” said Alessio Barbarulo, head of the local fire brigade division that coordinated the rescue effort.

As rescue services worked, the crushed wreckage of the coach lay on its side. Bodies covered in white sheets were lined up on the road before being taken away by ambulances.

There was some initial confusion over the number of casualties but a police official said 38 people died in the accident. Thirty-five were killed immediately and another three died later in hospital, he said.