Fire investigators are trying to determine the cause of a blaze that ignited in a home in Defiance early this (Tues.) morning.  The structure was unoccupied and owned by Marcus Gonzales in the 600 block of Ralston Avenue.   Crews were called to the scene just before 5am, and found flames coming from the second floor of the house, where the fire started.  Highland Township and Noble volunteers joined Defiance fire-fighters.  No injuries were reported; and its likely the damage is in excess of $35,000.  The state fire marshall’s office is investigating how the blaze started.