A fire that destroyed a southern Door County house is suspected to have originated in the fireplace.  The home of Jerry and Mary August on Lower LaSalle Road in the town of Clay Banks was fully engulfed in flames shortly after 9 pm on Saturday.  The Augusts were able to escape the fire by the time the Southern Door Fire Department responded to the lakeshore property.  Firefighter Chuck Cihlar says automated mutual aid was received from Sturgeon Bay, Brussels-Union-Gardner, and Algoma fire departments.   The fire was fully extinguished some three hours later.  The home is a complete loss but a detached garage was not damaged.  Cihlar adds that the fire call serves as a good reminder for homeowners to have their chimneys regularly inspected for cracks and that flues are replaced when needed.