PLUM, Pa. (AP) — Pennsylvania officials say it’s unlikely that natural gas seeped from an abandoned underground mine and caused a house explosion last weekend that killed six people. The state Department of Environmental Protection said Friday that its inspectors studied the coal seam in the area and found no shafts or bore holes near the house that exploded. The blast destroyed three structures and damaged others. The cause remains under investigation. The development is on abandoned mine land surrounded by shallow oil and gas wells. The state is looking for potential sources of combustible natural gas such as landfills, sewer lines, wells, pipelines and coal mines.