Unknown component that failed. Suspicion, the fuel system located at the back of the fire wall on drivers side. The fire started in that location and was extremely hot and fast moving. The truck was fully engulfed within 1.5 minutes then burnt the attached 5th wheel trailer and contents. It was a total loss of 3 vehicles 2018 Ford F350, 2021 Dutchman Voltage 5th wheel trailer, and a 2013 Polaris RZR side by side UTV. All was reduced to rubble within 15 Min. Our safety and lives were at risk, we had 30-45 seconds from smelling and seeing smoke to flames. We were traveling on Interstate 15 at highway speeds and had to stop as safe as possible on the shoulder of the road. The vehicle has not been inspected as far as I know, the frame is all what is left. There were no warning lights and all gauges read normal,