An envelope sent to the White House earlier this week has tested positive for cyanide and further tests will be carried out to confirm the finding , the Secret Service has said . On Monday , an envelope containing an 'unknown milky substance , in a container wrapped in a plastic bag , ' appeared at the White House Mail Screening Facility , The Intercept reported . Though initial biological testing yielded negative results , chemical testing returned 'presumptive positive ' for cyanide on Tuesday , CNN reported . Secret Service spokesman Brian Leary told CNN that the sample was transported to another facility to confirm the results with a third round of tests . Tests underway : An envelope sent to the White House earlier this week has tested positive for cyanide , the Secret Service said Tuesday , and a third round of tests to confirm the finding will now be carried out . 'Milky Substance : ' On Monday , an envelope containing an 'unknown milky substance , in a container wrapped in a plastic bag , ' showed up at the White House Mail Screening Facility . The Secret Service will have no further comment because the investigation is ongoing . A law enforcement official said the mail handler suffered no injuries and there were no exposure concerns , Fox reports . An alert identified the return address on the envelope as that of a man with a previous history of incidents with the Secret Service dating back to 1995 , The Intercept reports . The man allegedly once sent a package to the White House covered in feces and urine . Then in a 2012 incident , the man sent a package to the White House containing mini alcoholic beverages . Suspicious letters often are sent to some of the country 's leading politicians , including the president . Some test positive for hazardous substances while others include threats of death or physical harm . History : An alert identified the return address on the envelope as that of a man with a previous history of incidents with the Secret Service dating back to 1995 . He has previously sent letters covered in urine . In June 2013 , a West Virginia man was indicted on charges of threatening to kill Obama and his family in a letter that included profanity and racial slurs . A federal judge later dismissed the charges after forensic handwriting analysis conducted by the Secret Service showed that Ryan Kirker , 20 , of McMechen , West Virginia , did n't write the letter . Two months earlier , letters sent to Obama , Republican Senator Roger Wicker and Mississippi judge Sadie Holland tested positive for the poison ricin . The letters addressed to the president and to the senator were intercepted before delivery , but one letter reached Holland . She was unharmed . James Everett Dutschke of Tupelo , Mississippi , pleaded guilty in January 2014 to sending the letters and was sentenced to 25 years in prison .
An envelope sent to the White House earlier this week has tested positive for cyanide and further tests will be carried out to confirm the finding . The mail handler suffered no injuries and there were no exposure concerns . Authorities say its sender has been mailing packages to the White House since 1995 including ones covered with urine and filled with alcohol .