I'M FIRE INVESTIGATOR REPORTING THIS INCIDENT. UNEXPLAINED FIRE FROM UNDERNEATH TRUCK NEAR GAS TANK AREA. VEHICLE HAD BEEN IDLED 1/2 HOUR AND DRIVEN AT HIGHWAY SPEEDS BEFORE AND AFTER THE IDLING PERIOD UNTIL FIRE DISCOVERED BY DRIVER. TRUCK HAD 15KMILES, REGULAR SERVICING, NO MECHANICAL PROBLEMS UNTIL FIRE. *TR