Security alert after cyanide found on envelope sent to White HouseSources are indicating that authorities are on High Alert as An envelope addressed to the White House has tentatively tested positive for cyanide. The letter was received on Monday at a facility that screens mail for the White House and is located away from the grounds of the executive mansion and its surrounding buildings in the heart of central Washington. The poison was found after two rounds of analysis and additional testing will be necessary to confirm the finding. Initial biological testing came back negative, said Secret Service spokesman Robert Hoback. But additional testing conducted yesterday returned a “presumptive positive” for cyanide. The sample has been taken to another facility for further testing.  The Secret Service, which is responsible for the safety and security of President Barack Obama and his immediate family, said its investigation into the letter was continuing. 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 other physical harm. FULL REPORT