Three rail cars derailed on a train in northwest Milwaukee County on Monday, starting a small brush fire that officials believe was caused by sparks. There were no injuries, no release of materials nor any hazardous materials involved in the small derailment on the Union Pacific railroad near North 107th Street and West Brown Deer Road in the town of Granville, a rail spokesman said. Milwaukee police, Milwaukee firefighters and firefighters from the North Shore Fire Department all responded to the 1:25 p.m. incident.