Fire has caused extensive damage to a medical office at 23 Ivy Street in Jamestown.  Flames were reportedly leaping from the building when firefighters arrived around 2:30 AM today.  Battalion Chief Sam Salemme says Fire investigators are beginning to make their way through what remains of the structure to determine what caused the fire.  There were no reports of anyone in the building at the time. One firefighter suffered a minor injury.  The building on Ivy Street housed the offices of Drs. Jeffrey and David Krempa, and a podiatrist Dr. John Susz. As a result of the fire, Foote Ave is closed between Barker St. and Cole Ave.  Expect traffic delays in that neighborhood for awhile.