Sumwalt said the NTSB investigation to determine a likely cause will include routine testing of railroad employees for drugs and alcohol, testing of the track and rail signals and examinationof the video footage from the front of the train.

WSJ: Mo. highway buckles after rail cars hit overpass

Other complaints include that the series of downgrades spreads fear of a domino effect across Europe that could cause a double-dip in EU economies.

FORBES: Rating Agencies: Damned If They Downgrade, Damned If They Don't