Washington (CNN) Federal authorities secured an indictment on Thursday against a man accused of sending threatening letters to top US officials, including a ricin-related threat to President Donald Trump.

The Justice Department announced the indictment of seven counts against William Clyde Allen and said the indictment includes an allegation that Allen "knowingly threatened to use a biological agent and toxin, specifically ricin, as a weapon."

Allen pleaded not guilty to all charges on Thursday morning, according to the statement from the Justice Department.

The statement said Allen was also charged with mailing a threat against the President and was facing five counts of mailing threats to officers and employees of the US. It listed the officials threatened as Defense Secretary James Mattis, chief of naval operations Adm. John Richardson, FBI Director Chris Wray, CIA Director Gina Haspel and Air Force Secretary Heather Wilson.

The Justice Department release on Thursday said the letter addressed to Trump contained castor bean material. Ricin is a highly toxic compound extracted from castor beans.

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