A letter mailed to the White House this week has tested positive for cyanide, according to the Secret Service.
The letter never actually made it to the White House, instead as NBC News reported, the envelope with the unknown substance arrived at a facility which screens the mail first. A chemical test was done on the envelope and concluded that it was positive for cyanide.
CNN noted that the Secret Service confirmed the news in a statement on Tuesday.
"On Monday 3/16/15, an envelope was received at the White House Mail Screening Facility. Initial Biological testing was negative; however, on 03/17/15, the chemical testing returned a presumptive positive for cyanide," said Secret Service spokesman Brian Leary.
Since the investigation is still ongoing the agency would not comment further.
The Intercept website said that the return address is to a man who has a record with the Secret Service going back 20 years. The person has often attempted to send packages to the White House including one covered with urine and feces and another containing alcoholic beverages.