Thirty-four senators returned to their offices in one Senate office building Wednesday after health officials declared it anthrax-free.

Observers said it marked the first step towards a 'return to business' attitude Congress has been trying evoke since anthrax was found in the offices of Senate Majority Leader Tom Daschle, D-S.D, Oct. 15.

The White House also maintained a business as usual approach Wednesday after officials announced that a remote mail processing facility that serves the White House had tested positive for anthrax.

White House spokesman Ari Fleischer said preliminary tests on approximately 120 workers at its mail facilities showed none had been exposed to the potentially deadly anthrax bacteria.

Another 80 workers were being tested Wednesday and all 200 staff were given the antibiotic Cipro as a precaution, he said.

The office of the Senate physician also announced late Wednesday that after preliminary environmental and nasal swab testing, he has determined it is safe for senators or their designated staffers to enter Hart and Dirksen Senate office buildings to grab materials they may need to conduct business. The physician said the southeast quadrant of Hart was still off limits.

Daschle said Dirksen, where the mailroom also tested positive for anthrax, may even be ready to open as early as Friday.

U.S. Capitol Police Lt. Dan Nichols said authorities haven't decided how to clean up the Hart Building. That's where aides to Daschle opened the anthrax-laced letter last week.

Temporary drywall has been erected to seal off the hallway that connects Russell and Dirksen.

Slow Return to Normal

People working in Russell said they were given the all clear but not told how individual offices were examined.

Sonya Sotak, a legislative aide to Sen. John McCain, R-Ariz., returned to Russell Wednesday and said everything seemed to be as it was left when the building closed last Wednesday night.

"Unfortunately, they didn't clear it or throw away anything," she said, gazing at the pile of papers.

Russell houses offices for 34 out of 100 Senators. That means for the 66 senators who call the Hart and Dirksen Office Buildings home — and all the members of the House — it's another day working out of those makeshift offices inside the Capitol and at Congress' General Accounting Office.

Offices have been closed since last Wednesday when officials decided to conduct an environmental sweep after a staffer in Daschle's personal office opened up a letter containing anthrax. Another unopened letter was then discovered in the administrative office of House Speaker Dennis Hastert, R-Ill.

In total, investigators found four of the Capitol buildings to be contaminated with anthrax. The Capitol building was cleared and opened for business Monday.

House leaders are hoping to begin the process of re-opening some of their buildings on Thursday. They were subjected to a landslide of bad press and ill will when they decided to adjourn last Wednesday while the Senate continued to work.

The White House also fought off bad press Wednesday. Officials said no letter containing anthrax was ever sent to the White House, but a letter may have been cross-polluted when passing an anthrax-ridden letter at Brentwood mail facility, which processes all mail sent to Capitol Hill and the White House.

Law enforcement officials said that three to eight workers on loan from the U.S. Postal Service to Bolling Air Force Base where the Secret Service opens and inspects mail for the White House, had access to a contaminated machine. A trace amount of anthrax — between 200 and 500 spores — was found there.

Workers have exhibited no symptoms, and officials said that at least 8,000 spores must be inhaled into the lungs to get the most deadly form of anthrax. Substantially fewer spores can cause the highly treatable cutaneous form of anthrax if they enter a cut in the skin.

The air base is located on the Potomac River and shares property with the Anacostia Naval Station, miles from the White House.

Mail delivery to Capitol Hill and the White House is on hold until further notice. Daschle warned earlier this week that some of the mail on Capitol Hill might have to be destroyed.

Adding to the hysteria Wednesday was a letter addressed to the Jewish service group B'nai B'rith and dropped on the ground outside the General Accounting Office, where House members have temporarily set up work space. Police were summoned to the scene but Lt. Nichols said tests on the envelope revealed nothing dangerous.

Postmaster General John Potter also set off a furor when he said there was no guarantee that U.S. mail was safe.

Seeking to reassure the public, Bush said the administration was doing "everything we can" to avert additional attacks.

"The American people should presume that their mail is overwhelmingly safe. But everybody needs to be alert because we're a nation that's at war," Fleischer said.

The anthrax outbreak that has plagued Washington seems to have originated in the Brentwood mail processing facility. Some 4,000 workers at the city's postal facilities were being tested for exposure to anthrax following the deaths of two postal workers who served in the city's main mail processing center in the northeast Brentwood neighborhood. Nearly a dozen others are being treated for suspicious symptoms.

The Associated Press contributed to this report.