FORT FRANCES, Ont. -- A century-old rail lift bridge that crosses the U.S.-Canada border near the cities of International Falls, Minnesota, and Fort Frances, Ontario, has collapsed, and it's unclear when the area will reopen to water traffic along the Rainy River.

No trains were involved, and no one was injured in Wednesday's collapse, according to the Minneapolis Star Tribune. The cause is under investigation.

Some “biodegradable, non-toxic hydraulic oil” was released, but environmental crews have contained it and are working to recover the fluid, the Canadian National Railway said.

Crews have begun repairs to the structure, which was built in 1908. It's known as the Rainy River Rail Lift Bridge and the 5 Mile Bridge, and swings up to let traffic through on the river that forms the international border as it runs from Lake of the Woods to Rainy Lake.