Immigration officials say they apprehended a woman at the US-Canada border who was trying to enter the US from Canada after she allegedly sent a package of ricin poison to President Donald Trump. 

The woman, whose name has yet to be released by authorities, was discovered at a border crossing in Buffalo, New York and was reportedly carrying a gun. 

The letter that authorities believe she sent was on its way to the White House when authorities discovered it and took immediate action to prevent it from getting to the president.  

The letter remains under investigation by The Federal Bureau of Investigation (FBI) and the Secret Service.

Over the weekend, the FBI told CNN, "At this time, there is no known threat to public safety," 

CNN also reports that the woman may have sent additional packages with ricin poison to a jail and a Sheriff's Office in Texas. 

Ricin is most commonly described as a highly toxic protein obtained from the pressed seeds of the castor-oil plant. According to the CDC, once it's inside the cells of a person’s body it stops them from making the proteins they need, causing the cells to die. Eventually this is harmful to the entire body, and can result in the person's death.