Most fires are started by something natural or manmade. But sometimes there are fires that start without any obvious explanation. Theories abound from poltergeists and magma to high intensity electromagnetic radiation. Here we start with a few to wet your appetite: http://listverse.com/2013/06/29/10-mysterious-fires-caused-by-ghosts/ "Calvin Tuck, his wife, and six children suffered an ordeal by fire when their four-room house (not wired for electricity) became the target of an apparent poltergeist. In a short period, 52 fires were set. Some happened in front of eyewitnesses, who said the fires were reddish in color and smelled like sulfur. One of the strangest incidents was when a loaf of bread on a table spontaneously burst into flames. When the house was gutted by an uncontrollable fire, the Tucks moved to a new residence, but the fires continued. They left to occupy a third house. Five fires broke out on the first day and more followed. When their fourth house was plagued by fires, authorities coerced a confession from one of the children, though the “confession” was doubted by the many witnesses including police officers, firefighters, and reporters." ============================================================ "The Willey family in Macomb, Illinois, endured hundreds of fires in a two week ordeal which destroyed their home, two barns, and damaged the milk house. The inexplicable fires began as brown spots on the wallpaper which burst into flames. In the following week, they extinguished more than 200 fires in the home—which wasn’t wired for electricity, ruling out faulty wiring as a cause. The Willeys moved into a makeshift tent just in time—the very next day,their house was destroyed in a blaze. The following day, their first barn burned to the ground. An investigation by the state fire marshal yielded no explanation, although US Air Force officials believed the fires might be caused by radio waves, radioactivity, natural gas, or “atomic energy.” ============================================================ "Mike Parsons and his family’s ordeal began when his wife found a dictionary smoldering in the wood-box—while all the wood around it remained unburnt. Next, a sack of sugar in the kitchen burst into flames, but the fire went out as soon as Mike touched the sack. Subsequent incidents included a doll spontaneously consumed by fire while it sat in the middle of the floor, a box catching fire and burning a groove in a chest of drawers, and fires erupting in the corners of a bedroom without electricity or a fireplace. An RCMP investigation ruled out deliberate arson, but failed to find a cause. After a priest visited the house and performed a blessing, the fires stopped.The phenomena have never been explained."