An envelope that tested positive for a deadly poison was intercepted in a mail room at the U.S. Capitol.
Senate majority leader Harry Reid said the envelope was addressed to Senator Roger Wicker, a republican from Mississippi.
A lab in Maryland confirmed the presence of Ricin, a highly toxic substance derived from castor beans.
The chair of the Homeland Security Commission says it’s unlikely the incident is linked to Monday’s bombings.
A law enforcement source tells CNN that Senator Wicker has been assigned a protective detail.