The Russell Senate office building reopened Wednesday morning, the first of Congress' six main office buildings to unlock its doors since last week's anthrax incident. 
Thirty-four senators were able to return to their offices, but 66 others, and all the members of the House, continue to work out of makeshift offices. 
Even so, worries remain that the anthrax-laced letter sent to Senate Majority Leader Tom Daschle's office last week was not the only one that arrived on Capitol Hill. Those concerns were sparked by anthrax discoveries at a House mailroom and a U.S. Postal Service facility in town. 
"I would use as my working hypothesis that it's not the Daschle letter that caused everything we've seen to date," said Sen. Bill Frist, R-Tenn., a doctor who has been closely involved in Capitol Hill's response to its first bioterrorism attack. 
"I think we have to assume there is a possibility that other mail could be contaminated," said Daschle, D-S.D. 
No mail has been delivered to congressional offices since Daschle's letter arrived on Oct. 15. It is not known when deliveries will resume. 
Anthrax was discovered during the weekend on a machine that bundles mail for the Longworth House office building, creating suspicions that mail somewhere in the facility contains the bacteria. No such letter or parcel and no traces of anthrax have yet been found in Longworth, which like Congress' other office buildings has been closed since last week. 
All of Longworth's mail and some of Daschle's may be burned as a precaution, officials said. 
More tests throughout the Capitol complex revealed no new areas where the potentially deadly bacteria have been found. In addition, tests were completed on more than 5,000 congressional workers and others and the figure for those exposed to anthrax remained steady at 28, said Capitol Police Lt. Dan Nichols. 
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Daschle said authorities hoped to finish cleaning an anthrax-contaminated mailroom in the Dirksen Senate office building and reopen that building by Friday or Monday. Parts of the Hart Senate office building, where Daschle's office is, may begin reopening next week, he said. 
Cleaning contaminated areas could involve the use of noxious gases, bleach or other techniques. Daschle and others have said it could take weeks to completely reopen the Hart building. 
House leaders did not reopen any of their buildings Wednesday because they said test results were not complete. They hoped to reopen at least one building Thursday. 
Two sources, speaking on condition of anonymity, said the decision to reopen Russell overruled an initial recommendation from scientists and health officials who wanted it to remain closed while nearby buildings were cleaned. 
The House and Senate held sessions Tuesday, their first since 28 Daschle aides and other workers were found to have anthrax exposure. The House recessed last Wednesday and the Senate on Thursday. 
Their office buildings shuttered, members of Congress and their staffs are struggling to find places to work. Many aides worked from home, others from private offices, and some were given the day off. 
CBS News Correspondent Bob Fuss reports the most creative solution may be that of New York Democrat Gary Ackerman, who parked his station wagon on the Capitol plaza, set up a card table and some chairs and put up a sign, saying "Congressman Ackerman's Office."