COPENHAGEN — At least six people were killed in an accident involving two trains in Denmark on Wednesday morning, shutting down the primary artery linking the country’s two main islands for several hours.

The accident occurred shortly after 7:30 a.m., as a freight train and a Copenhagen-bound passenger train passed each other amid high winds on the Storebaelt bridge. But it was unclear just what happened, or how people died.

The deputy manager of Denmark’s Accident Investigation Board, Bo Haaning, told reporters at the scene that a cargo container carried by the freight train had somehow struck the passenger train. He said the trailer, which was apparently empty, had overturned or had been blown off the freight train.