Fairbanks Daily News-Miner: A wildfire that threatened a subdivision of about 20 homes near Anderson last week was caused by a burning underground coal seam, not a lightning strike as fire officials first suspected. ... A coal seam fire is the underground smoldering of a coal deposit that creeps along cracks in geologic coal structures. They often are originally started by lightning, grass or forest fires and can continue to smolder underground after surface fires have been extinguished, sometimes for many years.