Superior, WI (Northland's NewsCenter) - Around 5 PM Saturday five Burlington Northern Santa Fe cars derailed under the Belknap Street Bridge.
All, but one, were upright.
Sunday morning crews were working on cleaning up coal and getting the cars back on track.
BNSF officials say they are not sure what caused the derailment and are conducting an investigation.
They also say the incident did not happen on the main tracks of the train yard and has had minimal impact on their operations.
This is the second train derailment in Superior this month.