PASSENGER HEATED SEAT CREATED AN ELECTRICAL FIRE (NO FLAMES) ABOUT 30 MINUTES INTO TRIP. SEAT TOGGLE WAS SET AT "LOW". LEATHER WAS CHARRED, FOAM SEAT PADDING MELTED IN HOTTEST AREA OF THE BURN, PERSONAL PROPERTY ON THE SEAT WAS DESTROYED. THE TEMPERATURE OF THE HEAT MELTED A CD CASE AND PENS WHICH WERE IN A BAG ON THE SEAT. DRIVER RECEIVED BURNS ON FINGERS WHEN THEY BRUSHED AGAINST SEAT. GM HAS BEEN CONTACTED BY OWNER FOR ASSISTANCE. THE GM REPRESENTATIVE STATE THEY ARE UNAWARE OF ANY OTHER OCCURANCE. DT