Pascale Ferrier was arrested on Sunday at the New York-Canada border and is due to make her first court appearance in Buffalo.
The envelope containing the toxic substance and the threatening letter was addressed to the White House, but was intercepted at a mail sorting facility on Friday.
During the investigation, the FBI discovered that six additional similar letters appeared to have been received in Texas in September, according to court papers.
Those letters “contained similar language” to the letter that was sent to President Trump and were sent to people affiliated with facilities where Ferrier had been jailed in 2019.
Investigators also matched Ferrier’s fingerprints from four of the letters, the complaint said.
In Facebook and Twitter posts in September, Ferrier also wrote “#killTrump” and used similar wording as she did in the letter, calling him an “Ugly Clown Tyrant”, according to the document.
When she was arrested, Ferrier told Customs and Border Patrol agents that she was “wanted by the FBI for the ricin letters”, the complaint said.
Officers founded a loaded gun in her waistband and said she was also carrying a knife.
