Secret Service revealed the letter was sent to the White House on Monday. A biological test returned negative, but a chemical test done Tuesday confirmed the substance was indeed cyanide.
The package came with a letter and a plastic bag with a milky substance in a plastic container. Upon further investigation, the Secret Service discovered the parcel came from a frequent sender. The unknown sender has mailed items to the White House since 1995, including small alcohol bottles, urine, and feces.
While in nature small amounts of the chemical cyanide are linked to cherry pits and apple seeds, large amounts can cause convulsions and eventually death from respiratory failure.
An investigation continues.
SOURCE: NBC News | VIDEO: News Inc.