Washington (CNN) The White House received an envelope this week containing a substance that testing revealed to be cyanide, the Secret Service confirmed 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 in a statement. "The sample was transported to another facility to confirm the results." 
 
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 Leary said because there is an "ongoing investigation, the Secret Service will have no additional comment." 
 
 There were no injuries or exposure concerns for the person at the mail sorting facility who opened the letter, said a law enforcement official. 
 
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 An envelope sent to the White House Mail Screening Facility on Monday tested positive for cyanide, according to an internal law enforcement document obtained by The Intercept. 
 
 The envelope listed a return address for a man who the alert says has a record with the Secret Service dating back to 1995, which includes sending a package covered in urine and feces. 
 
 That person has sent multiple packages over the years; the most recent package was received on June 12, 2012, which contained mini alcoholic beverages. 
 
 “An envelope containing an unknown milky substance, in a container wrapped in a plastic bag, received at the White House Mail Screening Facility, tested positive for Cyanide,” the alert states. 
 
 The mail was received at the screening facility on March 15. Initial biological testing done the following day was negative. On Tuesday, however, the chemical testing returned positive for cyanide. 
 
 The sample has been sent to another facility to confirm the results. 
 
 The Secret Service did not immediately return a request for comment. 
 
 Photo: AP 
 
 Update: Secret Service spokesman Robert Hoback would not provide additional information, citing an ongoing investigation. In response to questions about the suspect’s status, he told The Intercept he did not know if the suspect was in custody, if the agency knew of his whereabouts, or had any contact with the man.
– An envelope addressed to the White House and apparently containing cyanide was caught by off-site screeners before it got anywhere near the president, the Secret Service says. A spokesman says the package initially tested negative for the poison after it was received at the White House Mail Screening Facility on Monday but it tested positive during chemical screening yesterday and a lab is working to confirm the results, CNN reports. Officials say that the person who opened the letter at the screening facility was not exposed. According to a law enforcement alert seen by the Intercept, the screening facility received an "envelope containing an unknown milky substance, in a container wrapped in a plastic bag." The alert says the return address belongs to a man who has been known to the Secret Service since 1995, when he sent a package covered in urine and feces to the White House. The person has sent other packages over the years, according to the alert, most recently "mini alcoholic beverages" in June 2012. (The Secret Service is seeking $8 million to build a fake White House.)