The Senate Sergeant-at-Arms office has received an all-clear after a false alarm prompted investigators in full-protective gear to conducts tests for the toxin ricin Tuesday morning. A later call from the Cannon House Office Building also turned out to be nothing serious.

The first incident occurred shortly before noon, when a staffer in the Sergeant-at-Arms office opened an envelope containing an unknown substance. The material in the envelope was not found to be toxic. “It was examined and declared negative,” Sergeant-at-Arms Bill Pickle said. “Something came out a residue, but it was not anything to be concerned about.”

Eyewitnesses told Roll Call that investigators in full protective gear entered the office; however, an aide who answered the phone in the office shortly before noon said staff had not been asked to evacuate. According to witness accounts, Senators and staff were also asked to vacate their first-floor hideaway offices during the testing.

All three of the Senate’s office buildings are closed today, pending the results of tests from a powdery substance found in Senate Majority Leader Bill Frist’s (R-Tenn.) office Monday afternoon. Initial tests suggest the material is ricin, a toxin derived from castor beans.

The Capitol Police, who are leading the investigation along with the FBI and the Homeland Security Department, expect results on additional tests conducted at Fort Detrick in Frederick, Md., this afternoon.

Then, after noon, a call came in from Room 212 of the Cannon Building when someone found a white powdery substance. The police department’s Hazardous Device Unit reported to the scene to conduct a test, which came back negative.

According to Sgt. Contricia Sellers-Ford, a Capitol Police spokeswoman, the department has received numerous calls today that resulted in negative test results.

“They’d rather be safe than sorry,” said Sellers-Ford.

— From staff reports.