According to its last filing with the EPA in late 2012, the company stated that it stored 540,000 pounds (270 short tons; 240 t) of ammonium nitrate and 110,000 pounds (55 short tons; 50 t) of anhydrous ammonia on the site.[18] A week after the explosion, Homeland Security Secretary Janet Napolitano told Senate investigators that the company did not appear to have disclosed its ammonium nitrate stock to her department. Federal law requires that the Department of Homeland Security (DHS) be notified whenever anyone has more than one ton of ammonium nitrate on hand, or 400 pounds (180 kg) if the ammonium nitrate is combined with combustible material.