A woman who is suspected of sending the package containing the deadly poison ricin to US President Donald Trump was arrested after she attempted to enter the United States from Canada through the border, a federal law enforcement official said.

The accused was arrested by US authorities and carrying a gun, the official was quoted by CNN as saying. She is expected to face charges. A person familiar with the probe told CNN that the package was mailed from St. Hubert, Quebec and contained a granular substance with similar physical characteristics to ground castor beans.