Capitol Police are questioning a man “who had numerous letters in a backpack,” and attempted to deliver them to the U.S. Senate today, according to Sen. Bill Nelson, D-Fla.

Nelson said “two suspicious items,” were removed from Senate office buildings.

Police earlier today gave an “all clear” signal to staff who were sheltering in their offices while the bomb squad checked out the suspicious packages, which were found in both the Hart and Russell office buildings.

Police and the FBI are currently testing mail sent to President Obama and Sen. Roger Wicker, R-Miss., that preliminary tests show may contain deadly ricin.