WHILE DRIVING VEHICLE OBSERVED SMOKE COMING OUT FROM THE LEFT SIDE OF DRIVER SEAT. SLOWLY FELT THE HEAT SENSATION GROWING STRONGER IN THE AREA. ALMOST IN A PANIC, AND AT GREAT RISK TO MYSELF AND OTHERS ON THE ROAD, TRIED TO NAVIGATE THROUGH TRAFFIC ON THE BUSY STREET, TO THE RIGHT HAND TURN LANE, WHILE TRYING TO AVOID WHAT WAS OBVIOUSLY GROWING INTO A FIRE IN THE SEAT. HAD TO AVOID SITTING IN THAT AREA OF THE SEAT, WHILE KEEPING THE SEAT BELT ON IN CASE THERE WAS A CRASH. FINALLY MADE IT TO A PARKING LOT AND JUMPED OUT. THERE WAS A HOLE IN THE LEATHER SEAT THAT WAS SMOLDERING. THE SEAT HEATER HAD BURNED A HOLE THROUGH THE LEATHER SEAT. TRIED TO FIND SOMETHING TO DOUSE IT OUT WITH BEFORE IT SPREAD TO OTHER PARTS OF THE SEAT. ALSO, DISCOVERED THAT MY PANTS WERE STILL SMOLDERING ON THE REAR LEFT LEG TOWARDS THE HIP AREA. THERE WERE TWO HOLES BURNED INTO THE PANTS FROM CONTACT WITH THE BURNING SEAT. CALLED THE DEALER AND SCHEDULED A SERVICE APPOINTMENT. CALLED BMW NA, WHO SAID THEY WERE NOT AWARE OF ANY OTHER SUCH INCIDENTS AND THEY WOULD HAVE TO WAIT FOR THE DIAGNOSIS FROM THE DEALER. THEIR ATTITUDE ALSO SEEMED VERY LAISSEZ-FAIRE ABOUT THE WHOLE THING, SEEMINGLY NOT TO CARE SINCE I WASN'T REPORTING ANY INJURIES. JUST THE FACT THAT MY SEAT WAS ON FIRE AND I BARELY AVOIDED GETTING IN A CRASH AND GETTING BURNED, WHILE MY PANTS ACTUALLY DID GET BURNED! MEANWHILE RESEARCHED THE INCIDENT AND FOUND ONE CASE REPORTED ON THIS VERY NHTSA WEBSITE, SEVERAL OTHERS ON THE X5 ON VARIOU