WARNING: Video contains expletive footage of the propane truck explosion, caught by nearby resident Kelly Scherfig. See details from a previous update below: DEVELOPING: At approximately 2:30 p.m., a propane truck caught on fire at the Kenyon Noble mix plant off U.S. Highway 191 near Big Sky. The fire extended to a nearby building, and the truck exploded, according to law enforcement officials. The highway is closed south of its junction with MT Highway 64, and officials say travelers can expect