An investigation is underway after a warehouse fire near Dermody Way between Nugget and Glendale Avenues Monday afternoon in Sparks. The area has been the site of five similar fires in the past three months. Last week the city took action, notifying the owner of the building that he needed to clean up the and secure the property.  The owner of the building, who lives out of state, has been cited in the past for building and fire codes.  Secret Witness is offering a $500 reward for information leading to arrest and prosecution for those responsible for the fires.