U.S. officials say the anthrax in a letter sent to a U.S. Senate office building was more deadly than traces of the bacteria found in New York. Three people have died, more than 30 people have been exposed to anthrax, and thousands are being treated as a precaution.
Homeland security director Tom Ridge says all of the anthrax is from the same strain, but the bacteria sent to Capitol Hill is more deadly because tests show it is smaller and easier to inhale.
"It shows that the anthrax in the letter received in Senator Tom Daschle's office has some different characteristics," Mr. Ridge said. "It is highly concentrated. It is pure. And the spores are smaller, therefore they are more dangerous because they can be more easily absorbed in a person's respiratory system."
The commanding general of U.S. army medical research. John Parker, says scientists could not carry out further tests on anthrax delivered to a newspaper office in Florida or to a television station in New York because not enough of the bacteria was recovered.
There was enough anthrax in a letter sent to the New York Post newspaper, however. And Major General Parker says that when it was compared with the anthrax sent to Senator Daschle's office, it was clear the samples were different.
"It appeared that the New York Post sample was clumpy and rugged and the Daschle sample was fine and floaty," he said.
Two of the people who died from anthrax were postal workers who investigators believe came in contact with the Daschle letter.
A mailroom worker for the U.S. State Department Thursday tested positive for anthrax and all State Department mail is now suspended. Another postal worker in New Jersey is also showing symptoms consistent with exposure to the bacteria.
Homeland security director Ridge says investigators are working around the clock to find the terrorists responsible for spreading anthrax through the mail.
"Based on these latest lab reports, it is clear that the terrorists responsible for these attacks intended to use this anthrax as a weapon," said Mr. Ridge. "We still don't know who is responsible, but we are marshaling every federal, state, and local resource to find them and bring them to justice."
Mr. Ridge would not respond to reports that anthrax spores from Senator Daschle's office were treated with a chemical additive produced only by Russia, Iraq, and the United States. The additive helps the spores remain suspended in the air, making them more easily inhaled.
There is no hard evidence linking the spread of anthrax with the terrorist attacks of September 11, but the Bush administration suspects both are the work of people with ties to Saudi dissident Osama bin Laden.
Mr. Ridge says additional testing may not lead investigators to the source of the bioterrorism. He said he does not know what countries or what facilities might have been able to produce this anthrax.
"Clearly, we are up against a shadow enemy, shadow soldiers, people who have no regard for human life. They are determined to murder innocent people," he said. "President Bush is very proud of federal, state, and local health care officials whose quick actions have no doubt saved many lives in the face of a new and horrible threat."
Mr. Ridge says more than 4,000 postal workers are being tested for possible exposure to anthrax. There will be environmental tests at 200 postal facilities on the East Coast and random testing at post offices nationwide.