Ammonium nitrate and regulated ammonium nitrate materials, while at all facilities whose owners and/or operators are required to be registered, shall be secured to provide reasonable protection against vandalism, theft or other unauthorized access. Such measures shall include, but not be limited to, ensuring that storage facilities are fenced or otherwise enclosed and locked when unattended and are inspected daily for signs of attempted entry, vandalism and structural integrity. An ongoing process of inventory control for ammonium nitrate and regulated ammonium nitrate materials stored at the facility shall be established and maintained.