On January 9, 2001, about 1050 Pacific standard time, a Cessna 402B, N6384X, sustained substantial damage during the landing roll-out at Ontario Municipal Airport, Ontario, Oregon. The airplane is registered to and operated by Ameriflight, Incorporated, of Burbank California, and was being operated as an instrument flight rules (IFR) supplemental cargo flight under the provisions of Title 14 CFR Part 135, when the accident occurred. The pilot and co-pilot were not injured. Instrument meteorological conditions prevailed and an instrument flight plan was activated. The flight originated from the regional airport at Baker, Oregon, approximately 20 minutes prior to the accident. There was no fire and no report of ELT activation. During a telephone interview with the fist pilot on January 23, 2001, he reported that the aircraft touched down approximately 1,500 feet beyond the landing threshold of runway 32. The runway is approximately 4,529 feet in length and was covered with approximately 1-2 inches of fresh snow. During the landing roll, approximately 100 feet from the end of the runway, the pilot applied braking action and attempted to exit the runway at the taxiway, however, the aircraft slid off the departure end of runway 32. The airplane's nose gear collapsed resulting in substantial damage to the fuselage. No mechanical malfunctions or anomalies were reported with the aircraft that may have contributed to the accident.