Front Seat Heater/cooler problems of the 2005 GMC Yukon

Car: 2005 gm Yukon denali occupants: father, driving; 16-year old son, passenger front; mother, left window seat middle row; 9-year-old daughter, lying on right and middle seats, of middle row. (daughter has cerebral palsy; unable to walk unassisted; wheelchair stowed in rear. ) both rear seat heaters on. Time: 9 a. M. 2/3/07 our family was almost 2 hours into a 3-hour trip, when I smelled an unusual odor. Thinking it was from outside, I tried to ignore for a few minutes, and then became overwhelmed by a noxious odor, and opened all windows. My husband pulled into a rest area on the florida turnpike about a mile later. Immediately when we parked, smoke began pouring out from under my daughter's seat. We frantically unbuckled her, as she has a disability. The smoke was very thick w/I a few seconds. We safely extracted her and all of us. My husband lifted her pillow, where she had been resting on the seat, only to find it charred underneath, and two gaping, still burning holes in the actual seat. He was eventually able to cut the seat heater cord and remove the cushion from the frame. Only 2 inches of pillow saved our precious daughter from being burned. In her words later, with limited speech, she told us she could smell the burning, but as unable to express it. The seat cushion had been out of the vehicle for nearly 30 minutes, as we were talking with emergency personnel, and incredibly, it began to smoke and burn again! they took no chances and doused it completely with water. GMC is now investigating.