 The investigators ruled out common causes of accidental fires , including electrical panels and furnaces . They determined that the basement level of the home , which contained the furnaces , had not been a point of origin , though two small orphan fires unconnected to the main burning had occurred in that area . Pour patterns were found on the ground and second floors , indicating that a flammable liquid had been poured there and covered many areas of the ground floor , blocked off the stairway from the second floor to the ground floor , and covered much of the hallway on the second floor . The pour patterns stopped at the door of the house 's master bedroom , but had soaked into carpeting in the hallway leading to the children 's bedrooms . Investigators could not determine the precise liquid used as an accelerant , though they proved that a can of gasoline the family kept in a shed had not been used . The amount of accelerant used was identified as between 3 and 10 US gallons ( 11 and 38 L ) . Concluding that the fire was a result of arson , the investigators on October 26 called in a second area task force , this one focused on homicide investigation . On October 27 , the district attorney for Johnson County was informed that the investigation was now criminal . 
