Letter to Obama contained poisonous ricin

A letter sent to president Barack Obama apparently contained ricin, the FBI has revealed.

Two letters with traces of the poison sent to the President and a US Senator are related, the FBI also said.

Both postmarked from Memphis, Tennessee, dated April 8 and say: “To see a wrong and not expose it, is to become a silent partner to its continuance.”

Both are signed, “I am KC and I approve this message.”

The FBI said the substance in the letters has preliminarily tested positive for ricin.

Both the letters to senator Roger Wicker, a Republican, and to Mr Obama were intercepted at off-site mail depots.

The FBI said there was no indication of a connection to the bombing at the Boston marathon.