TORONTO -- A Quebec woman accused of sending envelopes containing the poisonous substance ricin to the White House has now been charged with threatening U.S. President Donald Trump.

During a brief court appearance on Tuesday in Buffalo, N.Y., Pascale Ferrier of Quebec had a plea of not-guilty entered on her behalf. She is being held without bail and is due back in court on Sept. 28.

Ferrier, 53, wore a tan jail jumpsuit for the appearance, with handcuffs and a chain around her waist. She was also wearing a blue mask over her face.

Timothy Lynch of the U.S. Attorney's Office in Buffalo told the court that Ferrier should remain detained in the United States given the allegations against her and out of concern she might flee.

"The charge in the criminal complaint is a crime of violence," Lynch told the court. "The defendant is a serious risk of flight."

Ferrier was arrested at the New York-Ontario border on Sunday.

According to an affidavit filed on Tuesday by an FBI bomb technician, Ferrier mentioned that she may be "wanted by the FBI" for the ricin letters during her arrest at U.S. Customs. She was also carrying a loaded gun in her waistband at the time and had a knife on her person.

The affidavit also revealed portions of what was allegedly written in the letters.

In a letter addressed to Trump, the affidavit says, Ferrier told the president to "give up and remove your application for this election." She allegedly wrote that the ricin was her "gift" to him and if it did not work, she would find a recipe for another poison or use her gun against the president.

According to the affidavit, fingerprints belonging to  Ferrier were found on the envelope and the letter, as well as six similar envelopes and letters sent to addresses in Texas.

U.S. officials said the letter was intercepted on Friday before reaching its destination. All mail for the White House is sorted and screened at an offsite facility before reaching the president’s official residence.

During the investigation, the FBI say they discovered that six additional letters containing ricin appeared to have been received in Texas in September. According to court documents, those letters "contained similar language" to the letter that was sent to Trump and were sent to people affiliated with facilities where Ferrier had been jailed in 2019.

During her court appearance on Tuesday, Ferrier -- through an interpreter -- asked for an identity hearing, which would force the government to prove that she is the person for whom the arrest warrant was issued for, and a probable cause hearing, which forces the government to prove there is sufficient cause to proceed in the matter.

"She has a presumption of innocence and that'll be pursued further after today," Fonda Kubiak, the public defender assigned to Ferrier, told reporters outside the courthouse.

Kubiak added that Ferrier could be transferred to the District of Columbia after her hearing on Monday.

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 affidavit.

Ferrier, originally from France, became a Canadian citizen in November 2015 and is a computer programmer, according to sources.

She moved back to Laval last spring, weeks after being released from a prison in Texas.

Court documents show that in 2019, she was charged with unlawfully carrying a weapon and knowingly using a fake Texas driver’s license. According to arrest records, Ferrier spent three months in jail.

A team that specializes in biohazards swarmed a Montreal-area condo on Monday morning, evacuating several units as they looked for evidence connected to the ricin-laced letter sent to the White House.

The home is located in a multi-unit building on Vauquelin Blvd. in St-Hubert, Que., bordering a forest and not far from an airport.

RCMP said they didn't know if Ferrier lived at the condo, but added that there was a clear connection between her and the home.

"There's a link between the female suspect that was arrested in Buffalo, New York yesterday and this residence," RCMP Cpl. Charles Poirier said Monday, explaining to reporters in St-Hubert that police had a search warrant for the residence.

An RCMP team dedicated to chemical threats and explosives is leading the ongoing investigation, with support from local police and fire units.

Canadian law enforcement was called to help the FBI investigate after American authorities found evidence the ricin-laced letter to the White House had originated in Canada.

Ricin is a deadly substance extracted from castor beans. It is a plant that is not restricted and is easy to grow. With enough exposure, the poison can be fatal within 36 to 72 hours. There is no specific test for exposure and no antidote.

This isn't the first time a U.S. president has been sent ricin. Letters containing the substance and addressed to former president Barack Obama were intercepted on two separate occasions in 2013.

In those cases, each of the accused pleaded guilty to possession of a toxin for use as a weapon and received sentences between 18 and 25 years in prison.

None of the charges against Ferrier have been tested or proven in court.

With files from's Sarah Turnbull, The Associated Press and The Canadian Press