Warrensburg fire crews were called to a house fire just after 3 o’clock Sunday morning in the 700 block of South Holden. It was unoccupied at the time and both floors were involved. The structure had already suffered significant damage. Reportedly crews had to deal with the frigid overnight temperatures that hampered their efforts. After nearly four hours crews were still on scene and expect to open Holden Street this morning once crews are certain everything has been extinguished. The cause is still unknown and an investigation is underway.