The United States on Thursday posted a $1 million reward for information leading to the arrest and conviction of "terrorist" culprits who sparked a germ warfare alert by mailing anthrax.
FBI Director Robert Mueller said his agency and the US Postal Service were combining to offer the reward, part of an huge probe into the scare, in which news anchors, politicians and journalists have been mailed anthrax through the post.
Mueller announced "a reward of up to $1 million for information leading to the arrest and conviction of those responsible for terrorist acts of mailing anthrax."
Meanwhile on Thursday, senators filtered back to work in the face of an anthrax threat that prompted closure of the House of the Representative for a meticulous sweep by teams hunting for the potentially fatal germ.
Tests performed on some 1,200 people at the Capitol complex were likely to show at least a few more were exposed to anthrax, said Sen. Bill Frist, a doctor. He expressed confidence that early treatment would succeed against any who might be infected.
Tests have found that at least 31 people in a Senate office building across the street from the domed Capitol were exposed to anthrax Monday when a powdery substance fell from a letter to Senate Majority Leader Tom Daschle.
The threat prompted a divergent course at Congress - the Senate staying open for at least a limited session and the House closing until Tuesday.
It was believed to be the first time since British troops burned the Capitol in 1814 that danger to lawmakers forced a congressional recess.
Republican Sen. Susan Collins drove up to the Capitol on Thursday with an armload of outgoing constituency mail and some issue briefing papers.
"Most of us are only having skeletal crews today," she said. "But I think it's important that we're in session. It sends a strong signal that the terrorists or whoever is behind these attacks is not going to be successful in disrupting the government."
But House Minority Leader Richard Gephardt defended the "prudent and careful" decision to shut House operations.

"We're doing what any other building anywhere in the country should do" in a similar situation, he said. "We've got to resume normal life but we've got to be careful and vigilant and we've got to make sure we're not putting people in harm's way."
In what may be the first case of tainted mail outside the United States, officials in Kenya said Thursday a letter mailed to an unidentified recipient in their country from Atlanta has tested positive for anthrax spores.

In Washington, employees on Capitol Hill lined up Thursday morning for more testing and to receive an antibiotic if necessary.

"The terrorists are in a way making some progress here," Democratic Sen. Joseph Lieberman said on CBS's "The Early Show." "Have the terrorists ... created some fear? Yeah, they have. But ultimately they have created more unity in this country and on Capitol Hill than I have ever seen."

US officials say they do not know whether the anthrax exposures in Washington, New York and Florida were the work of foreign or domestic terrorists.

While the only known confirmed exposures were among Senate staff, House Speaker Dennis Hastert's employees had reported suspicious mail in their suite of offices Wednesday. Gephardt said a letter sent to Hastert or his staff was being tested for anthrax.

Attorney General John Ashcroft said the anthrax attacks could be the work of a group and individuals working independently.
"It may be that there is some of both here," Ashcroft said on PBS' "The NewsHour With Jim Lehrer."

In New York, an assistant to NBC news anchor Tom Brokaw was sickened after opening an anthrax-laced letter addressed to Brokaw, and a 7-month-old child of an ABC news employee in New York was found to have contracted the disease. The bacteria was found in New York state Gov. George Pataki's office and in a letter sent to a Microsoft office in the western state of Nevada.

At the federal Centers for Disease Control and Prevention, Dr. David Fleming said preliminary testing indicated the strain of anthrax found in the letter addressed to Brokaw "appears to match the strain in Florida." Fleming said it is not yet clear whether the Washington anthrax came from the same strain.

Maj. Gen. John Parker of the Army's testing laboratory at Fort Detrick, Maryland, said the powder in the Daschle letter contained a "common variety" of anthrax. But Scott Lillibridge, a federal expert on bioterrorism, said there's "been some attempt to collect it, perhaps refine it and perhaps make it more concentrated."

Three government officials said Wednesday there was no evidence of any foreign involvement in the powder contained in the letter to Daschle, although they continued to investigate that possibility. One official said there was evidence that could point toward a domestic culprit.

Sen. John Kerry said the letter to Daschle said: "You've been exposed to anthrax. You're going to die." He said the Daschle aide who opened the letter then dropped it, and others congregated around.
The American Medical Association urged physicians to quit prescribing unnecessary Cipro, an antibiotic used to treat anthrax, to Americans who might be stockpiling it as a precaution.
And the Food and Drug Administration said it was about to issue specific instructions on how to use two other widely available antibiotics - doxycycline and penicillin - to prevent anthrax infection.
Bureau Report