Senate Majority Leader Bill Frist announced progress in decontamination efforts at the Dirksen Senate office building, where the toxin ricin was found Monday. That facility will not open until next Monday, but another building closed as a precaution will reopen Thursday, and a third on Friday.

Law enforcement officials are investigating whether the ricin, which can be lethal if inhaled in great quantities, is linked to the same poison found in letters at postal facilities that serve the White House and a South Carolina airport in November.

The ricin on Capitol Hill was found in a mailroom of Senator Frist's office. Although investigators have not linked the incident to terrorism, Senator Frist said it was aimed to terrorize. "This is a terrorist attack on my life. I regard it as a terrorist attack on my life," he said.