Envelope with ricin intercepted at U.S. Capitol's mail facility

WASHINGTON, April 16 (UPI) -- An envelope sent to Sen. Roger Wicker Tuesday tested positive for the poison ricin at the U.S. Capitol's off-site mail facility in Washington, sources told CNN.

The envelope was intercepted before being delivered to the Missouri Republican's office and tested positive three times for the deadly poison, law enforcement sources told CNN and Politico. It was then sent to a lab in Maryland for additional testing.

Homeland Security Secretary Janet Napolitano and FBI Director Robert Mueller were briefing senators, Politico said.