An envelope sent to the White House that contained ricin has been intercepted by federal authorities, a U.S. official with information about the matter disclosed on Saturday.

The mail looks to have been delivered from Canada, a statement by the Royal Canadian Mounted Police, which said it was cooperating with the Federal Bureau of Investigation, said.

Based on the initial investigation, the mail tested positive for ricin, a waste product in the production of oil from castor beans, an official who requested anonymity and not authorized to discuss the ongoing probe said. No suspects have yet been identified.

Authorities are also conducting a probe into a possibly similar mail sent to authorities in Texas, reports said. A spokesperson for the FBI's Washington office bared the bureau, the Secret Service, and the Postal Inspection Service are examining a "suspicious mail" that was sent to a U.S. government mail center.

"At the moment, there's no known threat to public safety," the Wall Street Journal quoted the spokesperson as saying. All letters sent to the White House undergo a strict screening process done off-site.

A representative for Bill Blair, Canada's Public Safety Minister, divulged that the government's law enforcement units are now collaborating with their U.S. counterparts.

Concerns about the poison have sporadically surfaced in Washington. Authorities arrested a Navy veteran in 2018 who confessed to sending envelopes to U.S. President Donald Trump including members of his administration that contained a chemical from which the poison is derived. Authorities intercepted the letters, and no one was harmed.

In 2014, a Mississippi man was found guilty and given a 25-year jail sentence after sending letters laced with the poison to then-President Barack Obama and other White House officials.

Based on guidance by the Centers for Disease Control and Prevention, ricin works by penetrating the human body's cells and preventing them from generating proteins. Without the proteins, the cells perish. Ricin is harmful to the body, which could lead to death, the CDC said.

Ricin, if inhaled or ingested, can cause respiratory problems, diarrhea, nausea, and vomiting, No antidote for the poison has yet been developed, the CDC added.

According to medical experts, death from ricin can occur within 36 to 72 hours, depending on the amount of poison that entered the body and whether it is ingested, injected, or inhaled.

Ricin has also been featured in a high-profile case that could have been inspired by an espionage book: a 1978 London assassination of Georgi Markov, a Bulgarian regegade, who was pierced with an umbrella laced with ricin.