Pascale Ferrier, was taken into custody by U.S. Customs and Border Protection officers at the Peace Bridge border crossing in Fort Erie, Ont., sources have confirmed.
Earlier on Monday, the RCMP confirmed the suspect remains in FBI custody.
Ferrier was due to appear in court Monday but is now scheduled to appear on Tuesday at 4 p.m., the U.S. Attorney’s Office said.
Law enforcement officials told the Associated Press that she is expected to face federal charges.
Global News has also learned there is a major police operation underway in connection with the investigation.
The operation involves the RCMP and Canadian special operations forces, as well as public health. One of Canada’s highly secretive military counter-terrorism units is on the scene — the Canadian Joint Incident Response Unit (CJIRU). CJIRU is comprised of special forces operators who are experts in chemical, biological, and radiological threats.
A swarm of police teams arrived at a residential building on Vauquelin Boulevard in Montreal’s St-Hubert at 10 a.m. on Monday. A CBRNE (Chemical, Biological, Radiological, Nuclear and Explosive) team is leading the operation, which also involves local police and firefighters.
RCMP Cpl. Charles Poirier confirmed the search warrant concerns the “suspicious packages” sent to the White House and “other areas of the United States.” He said a number of surrounding units in the condo building have been evacuated as a precaution.
“There’s a link between the female suspect who was arrested in Buffalo, N.Y. yesterday and this residence,” he told reporters from the scene.
“We can’t confirm that it’s actually her residence. We know she’s linked to that address, but the nature of that link, that’s yet to come.”
A source with knowledge of the investigation says authorities have been intercepting cell phone calls and using signals intelligence in the investigation.
They are interested in knowing more about 13 people who have been in contact with each other who the source described as having “shared interests.”
RCMP said Sunday that “initial information from the investigation suggests the letter originated in Canada.”
Quebec Public Security Minister Genevieve Guilbault said she is following the “worrying” situation in St-Hubert, but would not comment further until the investigation had been concluded.
According to the RCMP, FBI analysis of the envelope indicated the presence of ricin, a potentially lethal poison derived from castor beans.
It was intercepted at a government facility that screens mail addressed to the White House and the U.S. president, a law enforcement source told the AP.
Other envelopes containing ricin were also mailed to law enforcement agencies in the Rio Grande Valley in South Texas, and the police in Mission Texas, according to an AP report citing law enforcement officials.
Letters were also sent to detention facilities in South Texas, another law enforcement official told Global News.
In a tweet Monday afternoon, Hidalgo County sheriff Eddie Guerra confirmed he and three members of his staff had been mailed envelopes containing ricin.
“No injuries were sustained,” the tweet read.
Guerra said he could not comment further due to an “active federal investigation.”
It’s unclear where the other letters originated from, or if the same suspect in custody is connected and to what degree.
Several sources told Global News that a final determination is still being made on the woman’s citizenship, as the arrested woman was classified as a U.S. person — someone who has either had American immigration status now or in the past or is an American citizen.
Read more: The deadly history of ricin
The sources previously told Global News Sunday evening that senior officials believed she was an American citizen, and confirmed that she was carrying a gun when she was arrested.
Sources told Global News that both Canadian and U.S. intelligence officials were aware of who this woman was.
Someone with the same name, who is also reportedly from Quebec, was arrested in Texas in 2019 on misdemeanor charges, according to Hidalgo County jail booking records.
The woman was charged with two counts of unlawfully carrying a weapon and one count of tampering with a government record.
She was released in May of 2019.
A Twitter account, showing the same name replied to a tweet asking someone to shoot U.S. President Donald Trump.
“I just read this tweet. I agree … Nobody did anything… It’s time to change! #killtrump,” the posted Sept. 9 reads.
The Twitter user follows 15 other accounts, all of which are related to U.S. and Canadian law enforcement agencies.
Among the accounts are U.S. Customs and Border Protection, U.S. Secret Service, the FBI, the U.S. Department of Homeland Security, Surete du Quebec and Sheriff Guerra.
Global News has not yet verified if the account belongs to the woman arrested in connection with the letters.
— With files from Global News’ Kerri Breen, Mercedes Stephenson and Hannah Jackson