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FBI launches 'intensive' anthrax investigation

Special Agent Hector Pesquera says the FBI has not found additional evidence of anthrax.

BOCA RATON, Florida (CNN) -- Federal agents investigating what they call a "limited" amount of anthrax at a Florida-based tabloid office began interviewing hundreds of people Friday in hopes of discovering the source of the bacteria.

FBI officials said they planned to interview more than 800 people -- including 300 people who worked in the building, as well as frequent visitors and employees' relatives -- about the nature and origin of the anthrax spores found at the American Media Inc. building in Boca Raton. About 100 FBI agents will conduct the interviews, which are set to run through the weekend.

"We've been conducting an intensive investigation to determine the source of the (anthrax)," said FBI Special Agent Hector Pesquera said Friday.

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The anthrax has claimed one life. Robert Stevens, a 63-year-old photo editor for The Sun tabloid, died last week from inhalation anthrax, contracted from breathing the deadly bacteria.

Two other employees -- mailroom worker Ernesto Blanco, 63, and Stephanie Dailey, 36, whose duties included some mailroom work -- tested positive for exposure to anthrax, but are exhibiting no symptoms.

Cases in Florida, N.Y.

Pesquera said the FBI's Boca Raton office is keeping a close eye on developments in New York, where an NBC employee in New York tested positive for cutaneous (skin) anthrax infection. It is considered less dangerous and more easily treatable than inhalation anthrax.

"We're in touch with New York; we are coordinating both investigations," said Pesquera, noting that New York investigators are in "the infancy stage" of their inquiries.

Florida investigators have detected anthrax spores on Stevens' keyboard and in a mailroom slot, officials say. More than 1,000 individuals have been tested for anthrax, with 965 results completed. From that number, only Dailey tested positive. Blanco, the other employee, was already hospitalized when the tests began.

As a "precautionary measure," Pesquera said authorities are also looking at three U.S. Postal Services in the area. Officials from the Centers for Disease Control and Prevention are talking to individuals at mail locations linked to the American Media building, testing some for anthrax exposure, he said.

American Media offices remained closed Friday, and employees worked from satellite offices while investigators scoured their building.

Authorities said it appeared that the same strain of anthrax is responsible for all three human exposures to the bacteria, as well as the spore discovered in the building. They could not, however, say with certainty if the strain was man-made.

In nature, anthrax spores are spread from the tissues of infected animals and can live in the soil for years. Some strains have also been developed in laboratories. A widely distributed form of anthrax, available to researchers for the past 50 years, originated at an Iowa laboratory.