US Defense Department personnel screen mail as it arrives at a US government facility near the Pentagon in Washington (Thomas WATKINS)

Washington (AFP) – Packages that were sent to the Pentagon this week have tested positive for a substance ricin is derived from, but not the deadly poison itself, an official said Wednesday.

The Pentagon’s mail screening facility on Monday intercepted suspicious packages addressed to Defense Secretary Jim Mattis and Navy chief Admiral John Richardson.

“It seems to be that it was a substance that ricin is derived from,” Pentagon spokeswoman Dana White told AFP. 

“It wasn’t ricin itself,” she added, stressing that the matter is still under investigation. 

Separately, the US Secret Service said it had obtained a “suspicious envelope” addressed to President Donald Trump on Monday.

“The envelope was not received at the White House, nor did it ever enter the White House,” the Secret Service said.

Produced by processing castor beans, ricin is lethal in minute doses if swallowed, inhaled or injected. It is 6,000 times more potent than cyanide, with no known antidote.

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