So far so good it sounds like. The Star Tribune reports that the train cars crushed by the collapsing bridge did not contain hazardous material and that the MPCA has not observed any sheen on the surface of the Mississippi that would indicate spills.
A second report in the Star Tribune mentions a car on the River Road was carrying a type of polystyrene and that other hazardous materials may be present, according to fire chief Jim Clack.
Update 8-10-07: Since this was posted, Minnesota Monitor and Outdoor News have also done stories.
Update 8-15-07: Minneapolis has a webpage dedicated to environmental concerns.