Six people were killed Wednesday after debris apparently from a cargo train smashed into a passenger train in high winds on a bridge connecting two islands in Denmark, the rail operator and officials said.

The passenger train appeared to have struck an empty truck trailer that had blown off a cargo train travelling in the opposite direction, as strong winds lashed the region.

The passenger train braked suddenly, survivors said.

“An empty truck trailer on a carriage seems to have fallen off. It either hit the train, or the train hit it,” accident investigator Bo Haaning told Danish public broadcaster DR.

He said it was too early to know why or how the trailer fell off.

“All I can say is that there is a trailer missing on the cargo train and there’s a trailer involved in the accident.”

Sixteen other passengers were hurt in the accident, but police said none had life-threatening injuries.

Police said the drivers of both trains were being questioned and video surveillance footage of the bridge was being examined to determine the cause of the accident.

Images from the scene showed the cargo train standing still on the tracks, the tarpaulin covers of its carriages torn open in places to reveal jumbled cases of beer, while the metal tracks appeared mangled in places.

An unidentified object — presumably the truck trailer — can be seen lying across the front of the passenger train on another track.

Rail operator DSB said six people died in the accident, which occurred around 7:30 am (0630 GMT) on the Great Belt Bridge connecting the islands of Zealand, where Copenhagen is located, and Funen. There were 131 passengers and three crew on board. (AFP)

• A passenger train is seen on the Great Belt Bridge after a railway accident on January 2, 2019 in Nyborg, Denmark. Mads Claus Rasmussen / Ritzau Scanpix / AFP

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