On April 15 , 2013 , an envelope that preliminarily tested Testing positive for ricin , a highly toxic protein , was intercepted Preventing_or_letting at the US Capitol 's off-site mail facility in Washington , D.C .

The dead Death comprised Cause_to_be_included 17 Christian pilgrims from Puerto Rico , a Canadian citizen , and eight Israelis , including Professor Aharon Katzir , an internationally renowned protein biophysicist .