I've seen a similar situation.
Occupant had an old A/C unit with 10 or 12AWG attached cord that he "twist spliced" to a dollar store type extension cord (16 AWG) to make up the three feet he was short to reach the outlet.
After we'd extinguished the fire, our investigators followed the "vee" to a spot behind the couch; they couldn't explain why the fire started 12" off the floor away from ashtrays or receptacles, until they found the ends of the cords met right at the point of origin.
One of our guys was amazed... "the first time in thirty years, and I finally got a real 'electrical origin' fire"...
