At 08:30 central time, a Cirrus SR-20 lost engine power and was damaged while landing in a field near St. Bonifacius. The pilot and passenger were seriously injured. The flight was en route from Minneapolis to Rapid City, S.D. Examination of the engine revealed three punctures in the top of the crankcase at cylinders number 1, 2 and 4. A 2-inch diameter piece of the crankcase rested on top of the engine. The oil drain plug was absent. The threads at the oil drain port showed no damage or evidence of safety wiring. There was no evidence of oil in the engine.