PRIOR TO ACCIDENT, VEHICLE HAD NO ISSUES AND WAS SERVICED ROUTINELY. THERE WERE 2 INDIVIDUALS IN THE CAR AND ACCIDENT TOOK PLACE ON A TWO LANE STATE ROAD APPROXIMATELY 2 MILES FROM RESIDENCE. THE WEATHER WAS HOT AND SUNNY ON THE MID-AFTERNOON OF THE ACCIDENT. DRIVER NOTICED SPUTTERING IN THE CAR AND DECIDED TO U-TURN TO RETURN TO RESIDENCE. AS DRIVER CONTINUED, SPUTTERING WORSENED AND SOMEBODY DROVE ALONGSIDE AND YELLED THAT THE VEHICLE APPEARED TO BE LEAKING GAS. VERY SOON AFTER, WHILE CAR WAS DRIVING AT 5MPH, THE CAR HAD AN EXPLOSION AND FLAMES CAME THROUGH THE PASSENGER WINDOW. BOTH DRIVER AND PASSENGER WERE BURNED AND MEDEVAC'D TO LOCAL BURN CENTER. PASSENGER RECEIVED SEVERE 2ND AND 3RD DEGREE BURNS ON UPPER HALF OF BODY. DRIVER ALSO RECEIVED BURNS BUT NOT AS SEVERE. EACH MANAGED TO EXIT VEHICLE BEFORE THE BEING ENGULFED BY FLAMES. VEHICLE IS COMPLETELY UNREPAIRABLE AND DESTROYED. FIRE MARSHAL REPORT AS FURTHER DETAILS ON POSSIBLE ORIGINS OF THE CAR FIRE.