WASHINGTON — An envelope received Monday at the White House Mail Screening Facility has tested positive for cyanide after chemical testing, the Office of Government and Public Affairs has confirmed.

Initially, biological testing was negative for cyanide but the chemical testing, done at another facility on Tuesday, returned a “presumptive positive.”

Robert Hoback, spokesman for the Office of Government and Public Affairs, says the Secret Service will have no additional as this is an ongoing investigation.