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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