Top federal law enforcement officials said Tuesday they do not have conclusive evidence linking suspected terrorist Osama bin Laden to envelopes of anthrax sent through the U.S. mail. The anthrax investigation continues and on an increasingly apprehensive U.S. public is looking for answers.

As they have for days now, government officials offered Americans a mix of reassurance and caution Tuesday.

With the public increasingly on edge over the anthrax scare, Attorney General John Ashcroft said so far investigators do not have any conclusive evidence as to who has been sending envelopes laden with anthrax spores through the mail.

"While we have not ruled out linkage to the terrorist attacks of September 11 or the perpetrators of that attack, we do not have conclusive evidence that would provide a basis for our conclusion that it is part of that terrorist endeavor," he said. "But make no mistake about it. People who send anthrax through the mail to hurt people and to invoke terror, it is a terrorist act."

The latest anthrax case involves a seven-month-old child who apparently was exposed during a visit to the ABC television newsroom in New York. The child is taking antibiotics and is expected to recover.

Meanwhile in Washington, police on Capitol Hill closed part of a Senate office building after tests confirmed the presence of anthrax spores in mail sent to Senate Majority Leader Tom Daschle.

The director of the Federal Bureau of Investigation, Robert Mueller, says investigators have little choice but to treat each report of possible anthrax exposure seriously. "Every threat is taken seriously. Every threat receives a full response," he said. "We have no choice but to assume that each reported instance is an actual bio-threat."

FBI Director Mueller says there are similarities between the letter send to Senator Daschle and one sent to NBC television anchorman Tom Brokaw. Both letters carried a postmark from Trenton, New Jersey, and contained similar markings.

At the Capitol, public tours have been suspended for the first time in recent memory and mail deliveries are being held up for security checks.

But Senate Majority Leader Daschle says lawmakers will continue to debate the nation's business. "I think what we have to do is not run away from these problems but address them, confront them, try to live our lives, do our work, carry out our responsibilities and that is what we are trying to do," he said.

But the anthrax scare may be taking a psychological toll on the public. On one hand, Americans have been told to carry on with their lives in as normal a fashion as possible. And most people are doing just that - going to work, heading to school or taking in football and baseball games.

At the same time, the FBI continues to warn about the possibility of additional terrorist attacks and the daily revelations about anthrax being sent through the mail have left many Americans jittery and apprehensive.

New York's irrepressible mayor, Rudolph Giuliani, is urging Americans to be aware of the anthrax threat, but not to over-react about it.

"The thing to emphasize is that we are talking about a very, very, very small number of cases and that all of this is treatable and very successfully treatable," he said. "And although people obviously are going to be concerned about it and they should, they should not be alarmed about it."

In the meantime, federal officials have issued a warning to those who have perpetrated anthrax hoaxes around the country, promising that they will be prosecuted and punished for sending fake anthrax letters. In one case, a Connecticut man faces charges after spreading white powder on a paper towel at his desk as an anthrax hoax. Eight hundred co-workers were evacuated in the wake of the scare and several of his colleagues had to be washed down with a decontamination solution. It is estimated that the disruption could cost the state government in Connecticut up to $1.5 million.