A letter addressed to US President Donald Trump found a deadly toxin called raisin. However, the letter was confiscated before it reached the White House.

The BBC reports that there is a separate office for testing before any letter sent to the White House is delivered. Officials said the matter was caught there.

The letter inside the envelope contained a deadly toxin called raisin. This raisin poison is made from the same seed that castor oil is made from. The US Centers for Disease Control and Prevention (CDC) says raisin is so toxic that just a few drops of salt can kill an adult.

When raisin is ingested, inhaled or injected, it causes dizziness and nausea. Then the limbs of the body become crippled. Death occurs within 36 to 72 hours, depending on how much raisin enters the body.

There is no antidote for raisin poisoning. Lab tests also detected the presence of raisins. There was no immediate comment from the Trump administration.

The FBI and the President's Secret Service are now investigating where the letter came from. The two agencies are also investigating whether a similar letter was sent to someone else.

The FBI told CNN television that it did not see any risk. Another official told the New York Times that the letter appeared to have been sent from Canada.

Meanwhile, Canadian police say they are working with the FBI to investigate the matter. The CDC says it can be used as a powder and spray weapon made of raisin.

The United States has previously sent letters to the White House containing raisins. A Mississippi man was sentenced in 2014 to 25 years in prison for sending letters containing raisin powder to former President Barack Obama and several other officials.

Four years later, in 2016, a former Army member was accused of sending a similar letter to the US Department of Defense headquarters and the White House.