Mine associates left the main office area and traveled to the mine work area at 6:20 a.m. One EE notified another EE at 6:25 a.m. by FM radio the mine office trailer had been destroyed by fire. The fire occurred sometime over the weekend. The mine was not in operation and no injuries. MSHA was contacted at 6:34 a.m. to report the fire. Cause has not been determined.