Corrosion was found in several railcars used on Amtrak's Borealis — the 7-hour and 24-minute train line from the Twin Cities to the Windy City.

Amtrak is resuming rail service on the popular Borealis line Thursday, using as bi-level railcars on the route between St. Paul and Chicago. Trains from the Windy City to the Twin Cities will begin rolling Thursday night with service in both directions expected to be back on track by Friday morning,

Amtrak’s daily Borealis service between St. Paul and Chicago was disrupted Wednesday, with buses replacing trains. The cause of the train cancellation was corrosion of passenger railcars used on the route. Amtrak made the announcement Wednesday morning and said the cancellation also affected its Downeaster, Hiawatha and Cascades service.