Ten empty BNSF Railway Co. freight cars derailed in a Spokane rail yard early today. The mishap did not affect the railroad’s main line, and crews expect to have the tracks cleared and repaired tonight. The derailment happened about 1:30 a.m. during a routine switching movement at the switching yard along East Trent Avenue, BNSF spokesman Gus Melonas said. A string of cars being switched hit two water tank cars on an adjacent track. Of the 10 derailed cars, five tipped on their sides, Melonas said. Cranes were used to lift the cars up and set them back on the tracks. “Crews are assessing mechanical damage,” Melonas said. There were no injuries and no hazardous materials involved, he said.