A woman suspected of sending a letter containing the poison ricin to President Donald Trump was arrested as she tried to enter the US from Canada at a border crossing in New York state, a US law enforcement official said.
The woman was carrying a gun and arrested by US authorities, according to the law enforcement official.
US prosecutors in Washington, DC, are expected to bring charges against her.
CNN previously reported that law enforcement had intercepted a ricin package sent to Trump last week, according to two law enforcement officials, and that investigators were looking into the possibility that it came from Canada.
A person familiar with the investigation told CNN’s Josh Campbell the letter was mailed from St. Hubert, Quebec, and contained a granular substance with similar physical characteristics to ground castor beans.
Two tests had been done to confirm the presence of ricin. All mail for the White House is sorted and screened at an offsite facility before reaching the White House.
A spokeswoman from the FBI Washington Field Office confirmed later Sunday that an arrest was made and that the investigation remains ongoing.
Ricin is a highly toxic compound extracted from castor beans that has been used in terror plots. It can be used in powder, pellet, mist or acid form. If ingested, it causes nausea, vomiting and internal bleeding of the stomach and intestines, followed by failure of the liver, spleen and kidneys, and death by collapse of the circulatory system.
As little as 500 micrograms, an amount the size of the head of a pin can kill an adult. There is no specific test for exposure and no antidote once exposed.
Ricin can be produced easily and cheaply, but experts say it is more effective on individuals than as a weapon of mass destruction.