One employee was infected with the skin virus while one other employee and three people involved in the investigation were exposed.
A police officer and two technicians who handled the contaminated letter were found with anthrax spores on them, but have not tested positive to the infection.
New York Mayor Giuliani said the police officer and one lab technician were found to have anthrax spores in their noses and another lab technician was found to have a spore on her face.
“When they were tested, minuscule spores were found,” Giuliani said. “They are being treated,” he said. “This does not mean they have anthrax.”
NBC announced on Friday that one employee had tested positive for the skin infection, but that she was responding well to antibiotics. Erin O’Connor, an assistant to NBC News Anchor Tom Brokaw, had handled two different letters containing powdery substances.
Further tests have shown that one letter containing a sandy substance, postmarked Sept. 18 from Trenton, N.J., tested positive for anthrax. A second, postmarked Sept. 20 from St. Petersburg, Fla. tested negative. The second contained a white powdery substance.
The other employee who was exposed to the letter has not tested positive for the disease.
O’Connor had apparently been suffering from a low-grade fever and a bad rash, common symptoms for the disease.