Filed at 2:33 p.m. ET

BOCA RATON, Fla. (AP) -- The FBI is investigating the possibility that the anthrax bacteria detected in two Florida men is a result of terrorism or criminal action, Attorney General John Ashcroft said Monday.

The bacteria that killed a man last week has been detected in the nose of a co-worker and on a computer keyboard in the newspaper office where both men worked, health officials said.

``We regard this as an investigation that could become a clear criminal investigation, and we are pursuing this with all the dispatch and care that's appropriate,'' Ashcroft said.

Asked if it was a terrorist-related investigation, he said: ``We don't have enough information to know whether this could be related to terrorism or not.'' He said the federal Centers for Disease Control and Prevention was providing expertise.

In Tallahassee, Lt. Gov. Frank Brogan confirmed to reporters that ``the FBI is in control of the investigation.''

The FBI sealed off the office building and was combing it for clues. Any workers in the building with flu-like symptoms will be tested for anthrax, officials said.

Bob Stevens, 63, a photo editor at the supermarket tabloid The Sun, died Friday. He was the first person in 25 years in the United States to have died from the form of anthrax that is contracted by inhalation.

Then, officials said Monday that a co-worker of Stevens, whose name was not immediately released, had been discovered to have the bacteria in his nasal passages.

Relatively large anthrax spores that lodge in the upper respiratory tract are less dangerous than smaller spores that get into the lungs.

The man has not been diagnosed with the disease, and Barbara Reynolds, a spokeswoman for the CDC in Atlanta, said authorities may never know whether he actually had anthrax because antibiotics may have killed it before it was detected.

David Pecker, CEO of American Media Inc., said the man worked in the mailroom and had been hospitalized with an unrelated illness. American Media publishes the Sun and other tabloids.

All 300 employees who work in the building housing the Sun tabloid were asked to come to a clinic so they could be tested for the bacteria. CDC officials said nasal swabs would be taken, and antibiotics provided. Anthrax cannot be spread from person to person.

Earlier Monday, White House spokesman Ari Fleischer would not rule out terrorism as a possible explanation.

``There is no evidence to suggest anything yet and that's why the FBI is investigating,'' Fleischer said. Health and Human Services Secretary Tommy Thompson had said last Thursday that Stevens' illness was ``an isolated case.''

There is particular concern about the origin of the anthrax, which is not normally found in wildlife or livestock in the state.

Stevens lived about a mile from an air strip where suspected hijacker Mohamed Atta rented planes, said Marian Smith, owner of the flight school, said Monday.

Several of the hijackers also had visited and asked questions at a crop-dusting business about 40 miles from Stevens' home.

The co-worker with the second case of anthrax was in stable condition Monday at an unidentified Miami-Dade County hospital, according to health officials. He had been tested for anthrax because he happened to be in a hospital and he was ill, authorities said.

A sample of anthrax was taken from a computer keyboard at the Sun, said Dr. John Agwunobi, the state's secretary of health. It was not immediately whose keyboard was involved.

``We have someone who has been exposed to bacillus anthracis, which is the spore which inhaled in a large enough dose could cause anthrax illness,'' Reynolds of the CDC said earlier.

State health officials set up a toll-free number that company employees could call to get information about health screenings.

Gov. Jeb Bush said the FBI is taking the anthrax investigation ``very seriously.''

When asked if it appeared to be a terrorist attack, Bush said, ``it's hard to tell right now.''

The Sun's offices have been shuttered and law enforcement, local and state health and CDC officials were to take additional samples from the building on Monday, said Tim O'Conner, regional spokesman for Florida's health department.

Some of the other environmental samples taken last week are still being tested, Reynolds said.

``The current risk of anthrax is extremely low,'' O'Conner said.

The anthrax bacterium normally has an incubation period of up to seven days, but could take up to 60 days to develop, O'Conner said.

Michael Kahane, vice president and general counsel of American Media, confirmed earlier that the company closed its Boca Raton building at the request of state health officials.

``We are cooperating with the department of health and all other governmental agencies investigating this matter,'' he said Monday. ``Obviously, our first concern is the health and well-being of our employees and their families.''

Only 18 cases of anthrax contracted through inhalation in the United States were documented in the 20th century, the most recent in 1976 in California. More common is a less serious form of anthrax contracted through the skin.

Anthrax can be contracted from farm animals or soil, though the bacterium is not normally found among wildlife or livestock in the state. Stevens was described as an avid outdoorsman and gardener.

County medical examiners are looking over any unexplained deaths, but have not found any cases connected to anthrax.

The largest experience with inhalation anthrax was in Russia in 1979, when anthrax spores were accidentally released from a military biology facility. Seventy-nine cases of anthrax were reported, and 68 people died.

An injectable anthrax vaccine has been around since the 1970s, and the U.S. military has required anthrax vaccinations for service personnel since the Persian Gulf War. Some have refused to take the injections because of severe side effects, which the Pentagon says happen about once per 200,000 doses.

^------

On the Net:

CDC: http://www.bt.cdc.gov/Agent/Anthrax/Anthrax.asp