The Waukesha Fire Department and Police Department are investigating the cause of an early morning fire in the 300 block of Arlington Street that displaced five families.  Today,at approximately 1:30, a fire was reported in a multi-family housing unit at 337 Arlington Street.  According to fire officials, when firefighters arrived, the residents had evacuated the building safely.   The fire was confined to the attic area of the building but damages are estimated in excess of $100,000.  Fire officials say the cause of the fire is suspicious in nature and is under investigation.  According to the Waukesha Police, a second fire was discovered on Dunbar Avenue, just west of Maple Avenue, which is in the vicinity of Arlington Street.  The Police are asking for anyone with information regarding these fires to contact Detective Mickiltz at the Waukesha Police Department.  Anonymous tips can be made through the Wisconsin Arson Insurance Council at http://wiarsonhotline.org/index.html.