A package addressed to president Donald Trump containing the poison ricin has been intercepted, according a report.
Two law enforcement officials told CNN that tests confirmed the presence of the poison.
Mail addressed to the White House is sorted and screened offsite.
The FBI and Secret Service are investigating the matter.
Ricin is found naturally in castor beans and can be made from the waste material left over when they are processed.
It can be in the form of a powder, a mist, or a pellet, or it can be dissolved in water or a weak acid.