The House suspended work and three Senate office buildings were closed yesterday as congressional leaders announced that 26 Senate staffers and five police officers had been exposed to anthrax spores that arrived in the office mail of Senate Majority Leader Thomas A. Daschle (D-S.D.) on Monday.

Almost simultaneously, New York Gov. George E. Pataki (R) added to the sense of national anxiety and confusion when he announced that anthrax microbes had been detected in his Manhattan office. Pataki and his staff began taking the antibiotic Cipro as a precaution.

The disclosures came amid growing evidence of connections between the anthrax sent to Daschle's office and similar episodes involving NBC News in New York and Florida tabloid publisher American Media Inc. Officials at the Centers for Disease Control and Prevention in Atlanta said yesterday that preliminary testing indicates the strain of anthrax that infected workers at the Florida firm, killing one, is almost identical to the strain that arrived in a letter sent to NBC.

FBI officials previously disclosed that the letters sent to Daschle's office and NBC bore Trenton, N.J., postmarks, were written in similar block letters and contained similar references to Allah, as well as warnings that anthrax was enclosed.

Seeking to calm public fears, officials emphasized yesterday that the anthrax sent to Daschle's office is a common strain that responds readily to antibiotics. But they also reiterated suspicions, first outlined on Tuesday, that the anthrax powder may have been produced in a sophisticated manner, so that it wafts easily through the air.

"There's been some attempt to collect it, prehaps refine it, and perhaps make it more concentrated," Scott Lillibridge, a bioterrorism expert at the Department of Health and Human Services, said at a hearing yesterday. "That seems certain."

Attorney General John D. Ashcroft tamped down expectations of arrests anytime soon, saying the government has not yet determined culpability for the Daschle letter or other anthrax contamination at three news organizations. The attorney general reiterated that investigators have neither found links to organized terrorist groups, including Osama bin Laden's al Qaeda, nor ruled them out.

Although no one has fallen ill from the anthrax sent to Daschle's office, yesterday's disclosures about the number of people who have been exposed to the spores on Capitol Hill -- a number that could grow with additional test results -- deepened the sense of alarm in Washington and across the nation.

At a late-afternoon briefing yesterday, Senate leaders and officials responsible for the anthrax investigation said that nasal swabs had turned up evidence of the bacterium in 23 Daschle staffers, three aides to Sen. Russell Feingold (D-Wis.), whose office is next to Daschle's, and five law enforcement officers who responded to the initial report Monday morning.

For the second day, hundreds of jittery staffers lined up yesterday outside a hearing room to submit to nasal swabs and receive precautionary three-day supplies of Cipro. But Deputy Surgeon General Kenneth Moritsugu said at the briefing yesterday that no other positive tests had turned up during the day and expressed confidence that "we will not see large numbers" of new exposures, although some more positives were possible. No spores had turned up in the ventilation system, he added, although the Hart building's mailroom had yielded a single positive test.

News of the exposures caused some degree of confusion in the Capitol as well as a rift between House and Senate leaders who seemed to have a different take on the situation. House Speaker J. Dennis Hastert (R-Ill.) generated a wave of anxiety when he announced erroneously that investigators had found anthrax "in the ventilation system."

Then House leaders made the decision to adjourn through the weekend so their side of the Capitol could be checked for anthrax, while their counterparts in the Senate pointedly declared their intention to remain in session through today. "We don't believe there's a rationale to shut down," said Sen. John F. Kerry (D-Mass.). The three Senate office buildings were closed to allow for additional testing, however.

Federal investigators examining the anthrax in the letter sent to Daschle are finding leads in their analysis of the material, said a senior federal bioterrorism expert yesterday. "We have substantive leads, and I regard that as very useful. These are leads in the sense of working with the material," said the official, declining to comment further on the probe in a briefing with reporters.

Ashcroft, interviewed on PBS's "NewsHour With Jim Lehrer," also said it is possible that individuals who sent the letters containing anthrax may be associated with some of the false anthrax threats that have swamped law enforcement officials this week. "There may in fact be some linkage," said Ashcroft. "There may be that people would do both."

Ashcroft said investigators are getting limited information from the hundreds of people taken into custody. "We've not been overrun with cooperation, which is not to say that we don't have some capacity to improve our awareness of what happened and what may happen," he said.

One law enforcement official said investigators continue to look strongly at the possibility that the attacks could be the work of a domestic terrorist.

The bioterrorism official said the FBI does not know at this point if the substance in the Daschle letter was "weapons-grade material," as some others in government have suggested, but he said the anthrax is "professionally made."

Weaponization involves processing anthrax with additives to keep it from clumping. It also involves creating spores of a size small enough to be inhaled but large enough to be retained in the lungs rather than exhaled. Samples of the specimens retrieved from Daschle's office and other apparent targets of reported attacks around the country have been sent to Los Alamos National Laboratory in New Mexico, which has more than 1,200 anthrax strains on file.

The anthrax criminal probe is being run as three separate investigations by FBI field offices in New York, Washington and Florida, officials said, with coordination from the counterterrorism division at FBI headquarters.

Bar codes and other identifying marks that appear on the envelopes sent to Daschle and NBC News anchor Tom Brokaw are being used to try to develop information about who might have mailed them, said postal inspector Tony Esposito. "We feel like we're making a lot of progress," he said late yesterday.

The letters passed through the postal service's processing and distribution center on Route 130 outside Trenton.

The bar codes -- including those that appear on the front in black ink and the fluorescent identification tags that appear orange on the back of an envelope -- indicate which machine at the facility processed a piece of mail and at what time.

By comparing those times with records of mail deliveries from branch offices, investigators have been able to narrow the geographic area they may have come from, Esposito said. He declined to say which branches investigators are focusing on.

Investigators also are reviewing post office surveillance videotapes and interviewing employees and customers.

The new cases reported yesterday bring to 45 the number of people -- in Washington, New York and Florida -- who have been exposed to anthrax. Of those, two people have come down with the most serious form of the disease, called pulmonary anthrax because it is acquired through inhalation. They are Florida photo editor Robert Stevens, 63, who died, and Ernesto Blanco, a 73-year-old co-worker at American Media who remains hospitalized.

Two more people have contracted the skin-transmitted form of the disease, which is less serious. They are Erin O'Connor, 38, an assistant to Brokaw, and the infant son of a producer at the rival ABC network in New York who apparently was exposed to the bacterium during a visit to the studio. Both are expected to recover. ABC offices in New York remain sealed off indefinitely as investigators seek to discover the source of the anthrax.

The CDC yesterday said preliminary tests had matched the anthrax sent to Brokaw with the strain of anthrax that killed Stevens in Florida. David Fleming, deputy director of the CDC, said in a telephone conference call with reporters that investigators had matched a fairly complete genetic fingerprint of the Florida strain with a small set of genetic markers from the New York strain. Comparable test results for the strain found in Senate offices are not yet available, he said. No anthrax has yet been recovered at ABC.

"The strain in New York, on the results of a small number of genetic comparisons, preliminarily appears to match the strain in Florida," Fleming said.

But investigators also had a new case to contend with yesterday. In New York, Pataki said anthrax spores were found on a hard surface in a small office in his Manhattan headquarters where his security officers usually sit. Officials evacuated Pataki and about 75 staff members from the high-rise building.

Health officials first tested Pataki's office after his secretary developed flu-like symptoms after handling a "suspicious" letter Sept. 25. The officials said the letter bore a New York state postmark and did not include threats. The secretary delivered the letter to the governor's police detail, but officials later determined the letter was not the source of the anthrax.

Aiming to alleviate heightening concerns about bioterrorism, New York Mayor Rudolph W. Giuliani said none of the nasal swabs taken from 500 NBC News employees last week had returned positive. Public health officials expected results from another 500 results from that network's employees to return late yesterday.

"It just reinforces the sense that this is a safe environment," the mayor said of the results.

ABC News President David Westin said in a statement that tests of air ventilation system filters at the network's midtown offices also showed no trace of anthrax bacteria. Still, employee testing continued, he said, adding that at least 150 employees so far voluntarily undergone testing for exposure to the bacterium.

After Friday's disclosure that anthrax had been found at NBC News, public health authorities conducted sweeps for anthrax in mailrooms at City Hall, the fire department, police department and other government agencies. Neil Cohn, the city's health officer, said "there's no public health concern."

At a news conference yesterday, Pataki added that state health labs are running 24 hours a day to handle the volume of anthrax testing. By Wednesday afternoon, the state health department had 74 different samples from ABC News to review. The state is moving workers dedicated to the West Nile virus to help test the large number of incoming samples, authorities said.

NBC said the powder that contained anthrax in the letter to Brokaw was brown and granular. When it was opened by a woman in the office, some of the brown powder fell onto her leg. She brushed it off and handed the letter, and a hate note inside, to O'Connor. The woman who opened the letter almost certainly developed symptoms of cutaneous anthrax as well, including a fever, black lesions and swollen glands. "She very much had symptoms of anthrax," said a spokesperson. "But it's been difficult to culture because she's on Cipro."

There is no connection between the information that prompted the Justice Department to issue a national warning of future terrorist attacks last week and the anthrax attacks, a law enforcement official said. The earlier warning was "time-specific" said a U.S. official, and was based on intelligence information generated by the wide-ranging investigation into the Sept. 11 attacks.

Staff writers Helen Dewar, Dan Eggen, Juliet Eilperin, Steven Gray, Michael Powell, Peter Slevin, Ceci Connolly, Justin Blum, Justin Gillis, Rick Weiss, Jo Becker, Fredrick Kunkle and special correspondent Christine Haughney contributed to this report.

Capitol Hill workers lined up for anthrax testing on the third floor of the Russell Office Building for a second day. Many workers waited in the line for more than three hours for testing.Postal inspectors enter the Manhattan building that houses offices of New York Gov. George E. Pataki after traces of anthrax were found in initial tests.