The national rail passenger agency said flooded highways have made providing bus transportation impossible in some areas.

The Empire Builder normally connects Chicago to Portland, Ore, and Seattle by way of Milwaukee and St. Paul, Minn. Until the flooding subsides, passengers will travel by bus from Chicago to St. Paul.

All service is suspended to Portage and Columbus in Wisconsin, while alternate rail service is available for passengers from Chicago to Glenview, Ill., and Milwaukee.

All service on the California Zephyr has been suspended in Iowa. Bus service is available from Chicago to Nebraska and Denver.

Amtrak is substituting buses for trains between Kansas City and Jefferson City, Mo., on the Missouri Mules because Union Pacific (NYSE:UNP) has detoured freight trains to the line.