A speeding work train slammed into a group of workers doing overnight track maintenance in northern Italy, killing five of them, authorities said.

The crash occurred shortly after midnight at the station in Brandizzo, a town in Italy’s Piedmont region.

Piedmont Governor Alberto Cirio provided the death toll and said the cause of the crash was under investigation.

Brandizzo Mayor Paolo Bodoni said there were indications that the crew of the train, which state radio said was believed to be going some 160 kilometres per hour (100mph), was unaware there were workers on the tracks.

A preliminary investigation by railway police later lowered the speed estimate to about 100 kilometres per hour (about 62mph), the Corriere della Sera newspaper said.

The train consisted of an engine car and 11 empty passenger cars that it was transporting.

Turin newspaper La Stampa reported that Mr Bodoni said: “The first information reaching me refers to a scarcity of communication between the (work) team and who should have signalled the passage of the train, but we need to see what really happened.”

Transportation and Infrastructure Minister Matteo Salvini said: “For sure there was a human error.”

Two workers who avoided being hit, were being treated for shock at a hospital, La Stampa said.

Various unions representing train maintenance workers vowed to stage a strike to protest the crash and to commemorate the victims, Italian media said.