Top FBI and CIA officials believe that the anthrax attacks on Washington, New York and Florida are likely the work of one or more extremists in the United States who are probably not connected to Osama bin Laden's al Qaeda terrorist organization, government officials said Friday.

Senior officials also are increasingly concerned that the bioterrorism is diverting public attention from the larger threat posed by bin Laden and his network, who are believed to be planning a second wave of attacks against U.S. interests here or abroad that could come at any time, officials said.

None of the 60 to 80 threat reports gathered daily by U.S. intelligence agencies has connected the envelopes containing anthrax spores to al Qaeda or other known organized terrorist groups, and the evidence gleaned from the spore samples so far provides no solid link to a foreign government or laboratory, several officials said.

"Everything seems to lean toward a domestic source," one senior official said. "Nothing seems to fit with an overseas terrorist type operation."

The FBI and U.S. Postal Inspection Service are considering a wide range of domestic possibilities, including associates of right-wing hate groups and U.S. residents sympathetic to the causes of Islamic extremists. But investigators have no clear suspects, and are not even certain whether there are other undetected letters that contained the deadly microbe.

But federal health officials said Friday that a new case of pulmonary anthrax in a man who worked at a State Department mail facility in Northern Virginia has persuaded them that more than one contaminated letter may have been sent to the Washington area. Health experts previously believed that a single letter, sent to the office of Senate Majority Leader Thomas A. Daschle (D-S.D.), likely caused all the anthrax reports in the Washington area as it came in contact with other pieces of mail in the system.

Now the "working hypothesis would be that this is not cross-contamination," said Jeffrey Koplan, director of the Centers for Disease Control and Prevention. "There is not enough infectious material from cross-contamination to do that."

However, ongoing searches of truckloads of undelivered mail to the U.S. Capitol and other government buildings has turned up no other letters laced with anthrax bacteria, leading FBI officials to assume that the Daschle letter may still be the only local source. Two employees at the U.S. Postal Service's Brentwood facility in Washington have died from inhaling the lethal bacteria, and three other local postal workers have contracted inhalational anthrax.

"This envelope, Daschle's envelope, is not watertight or airtight or anything like that," one law enforcement official said. "It's porous. At one or two microns, there's plenty of room for the spores to escape."

Although there is consensus at the FBI and CIA that al Qaeda associates are planning more serious attacks, "nobody believes the anthrax scare we are going through is" the next wave of terrorism, one senior official said. "There is no intelligence on it and it does not fit any [al Qaeda] pattern."

No links between known foreign terrorist groups and the anthrax letters have shown up on the daily Top Secret Threat Matrix, which includes the latest raw intelligence on potential bombings, hijackings or other terrorist attacks, one official said. Though "lots of things are alarming" on the list, there is little agreement on how, when or where an attack might be launched, officials said.

FBI Director Robert S. Mueller III warned last week that additional terror attacks are a "distinct possibility."

President Bush and other top U.S. officials have publicly voiced their suspicion that bin Laden and al Qaeda -- accused of carrying out the Sept. 11 suicide assaults on the World Trade Center and Pentagon -- may be responsible for the anthrax mailings.

But Mueller, Attorney General John D. Ashcroft and other law enforcement officials have said they have discovered no links between the mailings and bin Laden. Authorities, speaking on condition of anonymity Friday, said they are increasingly doubtful that any connections will be found.

One official said the only significant clue raising the possibility of foreign terrorist involvement is the conclusion of FBI behavioral scientists, who believe that whoever wrote the three letters delivered to Daschle, NBC News and the New York Post did not learn English as a first language.

But the writer could have lived in this country for some time, and the other evidence gathered so far points away from a foreign source, several officials said.

The anti-Israel message in the anthrax letters and bin Laden's statements are echoed by U.S. extremist groups, said Rabbi Abraham Cooper, associate director of the Simon Wiesenthal Center in Los Angeles.

One group, Aryan Action, praises the Sept. 11 attacks on its Web site and declares: "Either you're fighting with the jews against al Qaeda, or you support al Qaeda fighting against the jews."

Cooper said a meeting this year in Beirut was attended by neo-Nazis and Islamic extremists united in their hatred of Jews. "Some extremists are now globalized," he said.

White supremacists have been linked with anthrax in the past, but not in relation to an attack.

Larry Wayne Harris, an Ohio microbiologist and former member of the Aryan Nations, was convicted of wire fraud in 1997 after he obtained three vials of bubonic plague germs through the mail. He was arrested the next year near Las Vegas when the FBI acted on a tip that he was carrying anthrax. But agents found harmless anthrax vaccine in the trunk of his car.

Cooper and officials at the Southern Poverty Law Project, which monitors U.S. hate groups, said they have seen no evidence of a domestic group capable of launching a sophisticated anthrax attack.

One of the challenges that a would-be terrorist faces is learning how to alter the anthrax so that it will float in the air and disperse widely. The Washington Post reported last week that the spores in the Daschle letter had been treated with a chemical additive using technology so sophisticated that it almost certainly came from the United States, Iraq or the former Soviet Union.

White House spokesman Ari Fleischer said Friday, however, that investigators believe a broad range of people are capable of the crime. "The quality anthrax sent to Senator Daschle's office could be produced by a Ph.D. microbiologist and a sophisticated laboratory," he told reporters.

U.S. officials said the evidence so far does not point to either Russia or Iraq. However, FBI checks of private and government laboratories in the United States have not yet revealed any missing anthrax stockpiles, disgruntled scientists or other suspicious circumstances, one top official said.

Koplan, the CDC director, said he suspects more than one letter was involved based on his understanding of how difficult it is to contract inhalational anthrax. To cause the disease, 8,000 to 10,000 anthrax spores must enter a person's lungs.

Although some officials said it is possible for that many spores to have sloughed off the Daschle letter onto another piece of mail, Koplan said that is hard to imagine. "We all think that would be highly unlikely to virtually impossible," he said.

Koplan speculated that there may have been multiple mailings and that "there may be several places within the federal government that have been deemed targets."

By contrast, the minuscule amounts of anthrax bacteria discovered at Walter Reed Army Medical Center and the CIA "may well represent cross-contamination," Koplan said.

William C. Patrick, who is retired from the U.S. Army installation at Fort Detrick, Md., said extensive studies show that once anthrax spores hit the ground or other surfaces they stick, and are very hard to "re-aerosolize.

There's a theoretical possibility that a few spores picked up by an envelope might cause a skin anthrax infection, but a case of inhalational anthrax "is highly unlikely," Patrick said.

Staff writers David Brown, Ceci Connolly, Ellen Nakashima and Peter Slevin and researcher Madonna Lebling contributed to this report.

Anthrax was found in a letter mailed to the office of Senate Majority Leader Thomas A. Daschle.FBI Director Robert S. Mueller III warns that additional terror attacks are a "distinct possibility."