Envelopes with ricin were intercepted last week on their way to the White House, a sheriff’s office and a detention facility in Texas.
A Canadian national suspected of having mailed an envelope containing ricin to the White House was arrested on Sunday while trying to enter the United States from Canada, nearly a year after she had been deported from the United States for engaging in criminal activity, according to two American officials.
Customs and Border Protection agents detained the woman, who had a firearm, as she tried to cross the border into Buffalo, the officials said. Currently in the custody of border agents, she is set to be charged by the U.S. attorney’s office in Washington.
The suspect had been living in the United States last year and was arrested in March 2019 by the Mission, Texas, police for possession of an unlicensed weapon, resisting arrest and carrying a fake driver’s license, according to a senior intelligence official.
While in the Hidalgo County Jail in Edinburg, Texas, authorities discovered that she had overstayed her six-month visa and had violated the terms of her passport by committing a crime while in the United States, and she was deported back to Canada, the official said.
The Joint Terrorism Task Force in Washington has been leading the investigation into who sent an envelope containing ricin to the White House, addressed to President Trump, in recent days, as well as other envelopes containing ricin sent to a sheriff’s office and a detention facility in Texas.
Once discovered, the substance in the envelopes was confirmed to be ricin, a poison that is part of the waste produced when castor oil is made and has no known antidote.
Law enforcement officials said this weekend that the letters could have been sent from Canada, but that it was not clear when they were sent. The mail was intercepted last week, before it reached its destination.
No links to any international terrorist groups have been found, according to two law enforcement officials.
“An arrest was made of an individual allegedly responsible for sending a suspicious letter,” the F.B.I. said in a statement. “The investigation is ongoing.”
There were reports previously that the suspect had been detained.
The envelope addressed to Mr. Trump was intercepted at the final off-site processing facility before mail is sent to the White House mail room, according multiple law enforcement officials.
All mail sent to the White House and other federal agencies in the Washington area is irradiated by the Postal Service and sorted in a facility that samples the air for suspicious substances.
This is the second time someone has tried to send ricin to Mr. Trump. In 2018, federal authorities intercepted mail suspected of containing ricin that was addressed to Mr. Trump and to top Pentagon and other national security officials.
The Justice Department determined that the suspect, a Navy veteran named William Clyde Allen, had sent castor beans instead of ricin. He was charged in a seven-count federal indictment for threatening to use a biological toxin as a weapon.
Two people separately sent mail with ricin to President Barack Obama in the spring and summer of 2013. A Mississippi man, J. Everett Dutschke, received 25 years in prison for sending a ricin-laced letter to Mr. Obama and a Republican senator.
And an actress, Shannon Richardson, was sentenced to 18 years in federal prison for mailing letters with ricin to Mr. Obama and other public figures.