Investigators widen search for source of Capitol Hill ricin

WASHINGTON -- Investigators expanded their search Thursday for the source of ricin discovered on Capitol Hill after intensive testing of a Senate office mailroom failed to turn up the deadly poison's origin.

The ricin was discovered in Senate Majority Leader Bill Frist's office. Law enforcement officials say no letter or note has been found indicating how it got there, who was behind it and whether the Tennessee Republican was the target.

"We're not at the point in time where we can say how it was delivered," said Michael Mason, assistant FBI director in charge of the Washington field office. "We have not found a hot letter."

Mail has been the primary focus of the probe since Monday, when an intern found a small amount of ricin on a mail-sorting machine in Frist's office. But no further ricin or other evidence was in the stacks of letters nearby.

Because no answers have come from mail or items in the mailroom, investigators now must consider if the ricin was placed on the machine by someone or if it had spilled out of an older letter and been there for a long time. If so, investigators would have to trace the paths of these older letters, some of which may have been destroyed.

"We are taking a look at every possible angle," Mason said.

The discovery prompted the closure of three Senate office buildings, two of which reopened Thursday, and decontamination procedures for staff and Capitol police officers who were at the scene. Ricin is a highly toxic substance with no known antidote. It can easily be made from castor beans.

Although no one has become ill from the ricin, nine staffers in Frist's office have been asked to submit two blood samples to Navy medical researchers, Frist spokesman Nick Smith said. The aides were told it was to see if they had developed antibodies to the ricin, which might aid in development of an antidote.

Investigators are interviewing people who visited the buildings before the ricin's discovery, as well as employees. They described everyone so far as cooperative.

One Senate aide who was questioned and spoke on condition of anonymity said he had not been contacted for a second round and knew of no other staffers who were being questioned again.

The intern who found the ricin, described as a college-age woman, was credited by U.S. Capitol Police Chief Terrance Gainer with taking quick, decisive action when she found the substance.

"The young intern knew enough about precautions and to be wary to sound the alarm," Gainer said.

As the investigation progressed, life began returning to normal on Capitol Hill.

The Russell Senate Office Building, the oldest and closest to the Capitol, reopened shortly after noon Thursday. The Hart Senate Office Building opened later in the evening.

Hill workers waited in lines dozens deep in the winter chill to return to return to their desks.

"I'm anxious to get back to work because it's been so disorienting being out of my office," said Sen. Olympia Snowe, R-Maine, who has been working out of a Capitol office since Monday.

The Dirksen Senate Office Building, where the ricin was found, was scheduled to reopen by Monday morning.

The ricin investigation is not limited to Capitol Hill. Authorities are examining whether there is any link between the toxin found in Frist's office and that mailed in two letters by a self-styled "Fallen Angel" angered by new federal rules requiring greater rest periods for truck drivers.

Those letters were found Oct. 15 at a mail facility in Greenville, S.C., and Nov. 6 at an offsite location where mail is processed for the White House. The "Fallen Angel" author, claiming to be a tanker fleet owner, threatens in both letters to "start dumping" more ricin if the new rules are not repealed.

Gainer said investigators are not aware of any other communication from anyone called "Fallen Angel." But he added: "We are examining anything ricin-related."

FBI agents have interviewed truckers and owners of trucking companies.

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Associated Press writers Mark Sherman, Brad Foss and Nancy Zuckerbrod contributed to this story.

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