(Mosier, OR)  --  Union Pacific Railroad officials say they believe track failure led to a derailment that caused the oil spill and fire Friday near Mosier, Oregon.  Mosier Mayor Arlene Burns says the city council passed a resolution that calls for the railroad to halt train traffic until the derailed cars are removed and the investigation of the incident is completed.  A spokesman for Union Pacific says the track has been repaired and will undergo inspection and monitoring.