Ricin, a deadly toxin found naturally in castor beans, has been intercepted in a package addressed to Trump before it reached the White House, officials told US media.
The lethal substance is produced by processing castor beans. It infects cells, blocking their ability to synthesize their own protein.
If it is swallowed, or inhaled, it can cause nausea, severe vomiting, dehydration, internal bleeding and ultimately organ failure.
To date, no known antidote exists for ricin. If a person is exposed to ricin, death can take place within 36 to 72 hours, depending on the dose received, according to the US Centers for Disease Control and Prevention.