US authorities have intercepted an envelope addressed to President Donald Trump that contained a deadly poison called ricin, US media reported Saturday (local time).
The letter was discovered earlier this week and did not reach the White House, according to the New York Times and CNN.
The Times said officials believe the letter was mailed from Canada and have identified a woman as a suspect.
Mail addressed to the White House is first inspected and sorted in depots just outside Washington.
CNN said the contents of the envelope were tested repeatedly at one depot and confirmed to contain ricin.
"The FBI and our US Secret Service and US Postal Inspection Service partners are investigating a suspicious letter received at a US government mail facility," the FBI's Washington field office said in a statement.
"At this time, there is no known threat to public safety."
The White House and US Secret Service declined to comment.
Ricin, which is produced by processing castor beans, is lethal even in minute doses if swallowed, inhaled or injected, causing organ failure.
It has no known antidote.
There have been numerous incidents involving envelopes mailed with ricin to US officials.
In 2018, a Utah man, William Clyde Allen III, was indicted for making ricin-related threats, including mailing a threat against Trump and other federal officials including FBI Director Christopher Wray, with all the letters “containing castor bean material”. Allen remains in custody.
Two people were convicted in separate incidents of sending ricin-tainted letters to then-President Barack Obama.
In May 2014, a Mississippi man, James Everett Dutschke, was sentenced to 25 years in prison after pleading guilty to sending letters with the deadly substance to Obama, as well as a senator and a state judge.
In July 2014, a Texas actor was sentenced to 18 years for mailing letters containing ricin to Obama and former New York Mayor Michael Bloomberg.
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