FBI and health officials, who say they still have no evidence that the incidents in the three states are linked to the Sept. 11 terrorists or to one another, lead a criminal investigation that is rapidly widening in scope and complexity.
At a New York news conference yesterday, officials said a threatening letter addressed to NBC news anchor Tom Brokaw and postmarked Sept. 18 from Trenton, N.J., was the likely source of the anthrax that sickened an aide to the news anchor.
Initially, authorities had focused on a suspicious powder-filled letter sent from St. Petersburg, Fla., to NBC. But that letter - along with a similar one sent to The New York Times - tested negative for anthrax spores.
In Nevada, meanwhile, a letter sent to Microsoft Licensing Inc., a Reno subsidiary of the software giant, was found to be contaminated with anthrax, Gov. Kenny Guinn said yesterday. The letter, which contained a check from Microsoft to a vendor in Malaysia and pornographic pictures, had been tested twice before. Results had been inconclusive or negative.
Thus far, none of the six people who touched the envelope or were nearby when it was opened Friday are known to be infected or showing signs of illness, Guinn said. The letter is being sent to the Centers for Disease Control and Prevention in Atlanta for analysis.
"This is a very, very low risk to public health," Guinn said.
As criminal investigations in New York and Nevada get under way, federal agents in Florida continue piecing together how anthrax was introduced into the headquarters of American Media Inc., the Boca Raton publisher of the National Enquirer and other supermarket tabloids.
Investigators suspect that the deadly pathogen might have arrived in a letter or package because traces of anthrax were found in the company's mailroom and two mailroom workers were found to have been exposed to the bacteria.
The only other place anthrax was located in the building was on the computer keyboard of Robert Stevens, a photo editor who died Oct. 5 of inhaled anthrax, the most serious form of the disease.
Yesterday, the tabloid company learned from the CDC that five more employees had been exposed to anthrax, said spokesman Gerald McKelvey.
More than 1,000 employees and visitors to the American Media building have been given nasal tests for anthrax in the past week.
As a precautionary measure, CDC officials are also testing about 20 mail sorters who work at three post offices that serve American Media
In New York, officials are closely watching a second NBC employee who is exhibiting a fever, rash and other symptoms of anthrax. The employee, who has not been identified, is being treated with antibiotics while officials await test results.
About 200 NBC employees, including Brokaw, are being tested for exposure to anthrax since Brokaw's aide, Erin M. O'Connor, was found Friday to have developed the cutaneous, or skin, anthrax, a less serious form of the disease.
O'Connor developed a rash on her chest several weeks ago, health officials said. When it worsened, she consulted a doctor Oct. 1, who prescribed the antibiotic Cipro. Health officials learned Friday from skin biopsy results that she had anthrax.
O'Connor was one of several NBC employees thought to have handled the tainted letter, which contained a sand-like substance.
There was some confusion about why investigators in New York only learned about the Trenton letter yesterday, while the St. Petersburg letter sent to NBC Studios was turned over to the FBI on Sept. 26, the day after it was received.
NBC Chairman Bob Wright explained at a news conference that the Trenton letter was accidentally filed in a folder where the company keeps other threatening letters. Wright added that it was not unusual for employees to get such letters.
But after learning of the anthrax case Friday, FBI officials evacuated some NBC offices at their Rockefeller Center headquarters and began a criminal investigation. That's when they discovered the Trenton letter, which had no return address and contained threats that authorities would not specify. It is not clear when the Trenton letter arrived at NBC.
The discovery of the source of exposure provided some relief to nervous NBC employees. "Now we have identified the missing link, so to speak, the actual cause of the anthrax that created this whole situation," said Wright. "So we are no longer dealing with an unknown time, date and place and that is very important."
The New York Times briefly evacuated its Manhattan offices for several hours Friday after reporter Judith Miller opened an envelope containing a white powder. Like the letter sent to NBC, the envelope sent to Miller was postmarked in St. Petersburg, Fla.
The preliminary tests conducted on The New York Times letter by the New York City Department of Health were negative. Results from additional tests by the CDC were not expected until Tuesday, said Times spokeswoman Catherine Mathis.
The anthrax mail attacks in New York and Florida - and now Nevada - have continued to fuel fears across the country. Law enforcement agencies continued to be inundated by panic calls about suspicious mail and powdery substances.
A US Airways flight from Charlotte, N.C., to Denver was diverted yesterday to Indianapolis after a flight attendant found a powdery substance on the plane. Tests by the state health department found the substance to be harmless.
In Maryland, the New Market Post Office was temporarily closed yesterday when a postal employee noticed a suspicious letter addressed to the White House. The letter leaked a powdery substance and was "stained, had no postmark and no return address other than 'England,'" said Inspector Eric Kocay.
Frederick County sheriff's deputies were dispatched to the post office, along with FBI agents and members of the Secret Service. But the substance appeared to be nothing dangerous, according to the sheriff's office.
"We're answering some of the strangest calls we've ever received," said a Frederick County Sheriff's deputy. "One woman overheard two people not speaking English on her cell phone - and she wanted us to do something about it."
Another suspicious-envelope incident forced the evacuation of T. Rowe Price's Building Four at its investor center in Owings Mills yesterday around 10 a.m. Fire officials said an employee called police shortly before 10 a.m. and reported an envelope, in the mail room, with a "white powder" inside. The substance has yet been identified.
Hazardous materials crews arrived at the scene and turned over the envelope to the FBI for analysis. No injuries or symptoms were reported, fire officials said.
Federal officials warned yesterday that anyone caught perpetrating a hoax would be prosecuted.
Sun staff writer Michael Scarcella and wire reports contributed to this article.