"Initial information from the investigation suggests that the letter originated in Canada", RCMP spokesman Dan Brien said in an email on Saturday.
Authorities are investigating additional similar packages mailed to addresses in Texas that may be connected to the same sender in Canada, CNN previously reported, according to a USA law enforcement official.
On Saturday afternoon, the Federal Bureau of Investigation announced it was investigating a package with the U.S. Secret Service. They're working to figure out who mailed the letter and where exactly it came from. The woman is suspected to be the sender of a letter intercepted on its way to the White House containing the deadly poison, ricin.
The Commission signs Second Contract to ensure Access to a potential Vaccine
Sanofi and GSK started clinical trials of their vaccine this month and aim to reach the final testing stage by December. The deal also gives the USA government an option for an additional 500 million doses over the long term.
The police haven't revealed the number of letters found containing ricin.
Fictional character Walter White played by Bryan Cranston, the protagonist of Breaking Bad, had tried to use ricin to kill a major character on the show, Gus Fring, and was even suspected of poisoning a young kid with the poision. No known antidote exists. It is about 6,000 times deadlier than cyanide and can cause death within 36 hours with an amount as small as a pinhead.
Back in 2014, a MS man sent letters dusted with ricin to President Barack Obama and several other White House officials.
A Navy veteran was arrested in 2018 and confessed to sending envelopes to Mr Trump and members of his administration that contained the substance from which ricin is derived. Actor Shannon Guess Richardson was jailed for 18 years for sending the letters.