WASHINGTON (AP) – The FBI probed similarities Tuesday between an anthrax case in New York and a spore-spiked letter mailed to Senate Majority Leader Tom Daschle. Officials dispensed precautionary doses of antibiotics by the hundreds in the shadow of the Capitol.

”Obviously, these are difficult times,” said Daschle, as the Senate – and the nation it represents – grappled with the unsettling threat of bioterrorism.

A thousand miles to the south, Floridian Ernesto Blanco lay ill in a hospital with the inhalation form of anthrax, less than two weeks after a co-worker died of the same illness.

In New York, headquarters for many of the nation’s high-profile news media corporations, officials said they expected full recoveries for two people infected with a less lethal form of the disease. They included an NBC news employee and the 7-month-old son of an ABC producer.

Yet five weeks after terrorist strikes killed 5,000, the nation reeled under a continuing series of disclosures involving letters tainted by anthrax bacteria; spores discovered in a postal facility in Florida; countless innocent scares; and not a few malicious hoaxes.

Since Oct. 1, FBI director Robert Mueller said, ”the FBI has received more than 2,300 incidents or suspected incidents involving anthrax or other dangerous agents.”

Mueller told reporters there were ”certain similarities” between the letter opened at NBC and one unsealed in Daschle’s office across the street from the Capitol several days later. Both were postmarked in Trenton, N.J. – the NBC letter on Sept. 16 and the Daschle letter on Oct. 8. Mueller said there were similarities in handwriting, as well. Two officials, speaking on condition of anonymity, said the letters contained similar threatening messages expressing anti-American and anti-Israeli sentiments and included a pro-Muslim statement.

Authorities were also testing to determine whether the anthrax found in New York and in Florida were from the same strain, said Dr. Jeffrey Koplan, director of the Centers for Disease Control and Prevention.

In a chilling development, Sen. Olympia Snowe, R-Maine, who attended a closed-door briefing on the subject, said the strain of anthrax found in the letter to Daschle was ”very refined, very pure,” making it more dangerous. Daschle said he was told it appeared to be the work of experts.

Early testing indicates that the anthrax from Daschle’s letter is a purified form that can be used as a weapon, said a law enforcement official, speaking on condition of anonymity. Additional testing was being done late Tuesday.

Health and Human Services Secretary Tommy Thompson tried to reassure an anxious public the government has plenty of Cipro, the antibiotic dispensed to those who may have been exposed. The manufacturer, Bayer Corp., says it will produce 200 million more tablets in the next three months – and Thompson said Bayer promised not to raise its prices.

”I want to make sure that everyone understands we have enough antibiotics right now,” Thompson said.

His top health aides added that other antibiotics work against anthrax, too.

Investigators dispatched to a New Jersey mail processing facility scanned surveillance tapes and canvassed postal workers as they sought clues about the origin of the two pieces of mail. But officials said the letters could have started at any of 46 smaller facilities before arriving at the main post office. ”It’s difficult but not impossible” to determine the precise course each letter took, said Tony Esposito, a postal inspector.

Daschle said that thus far, none of the staff aides who had been in the area near the letter had reported positive for anthrax exposure.

But in steps that underscored the extraordinary level of concern, Capitol police cordoned off an entire wing of the eight-story Senate office building around the majority leader’s office so they could check for evidence of contamination. A dozen senators’ offices were temporarily relocated in the process, and mail shut down for the second straight day throughout the Capitol complex.

Officials invited aides, tourists, reporters and anyone else who might have been in the area Monday to report for nasal-swab tests. Anyone who did was given a three-day supply of antibiotics, six pills in all, and told to report back Thursday to obtain the lab results.

”We have to throw out the net as widely as possible,” said Dr. John Eisold, the Capitol’s attending physician. ”If we screen them, we treat them.”

Authorities moved aggressively elsewhere around the nation to trace the source of tainted mailings, and to respond to fresh threats.

City officials in New York conducted environmental tests at ABC offices, hours after the Monday night disclosure that the 7-month-old had become ill. There had been no previous publicly reported anthrax incidents involving the network, and officials said the boy became sick after spending time in the newsroom last month.

However, federal health officials said it was still unclear if the youngster contracted anthrax at the network offices or elsewhere.

With numerous media outlets affected directly, New York City health officials began making the rounds Monday night of the mailrooms of The Associated Press, major television networks and newspapers.

Mueller told reporters that so far, federal investigators have found no ”direct link to organized terrorism.” Daschle, S-S.D., added, ”I’m not at all sure that all of this is related directly” to Osama bin Laden, the suspected mastermind behind the Sept. 11 terrorist attacks that slaughtered thousands in New York and Washington.

President Bush said Monday he wouldn’t rule out a connection to bin Laden. But administration officials said they were also investigating to see whether there was a connection to Iraqi President Saddam Hussein.

At a news conference in Washington, Attorney General John Ashcroft condemned anthrax hoaxes as ”grotesque transgressions of the public trust.” He announced the indictment of a Connecticut man, Joseph Faryniarz, for making false statements to a federal agent in connection with a hoax at his place of work.

Ashcroft said false threats ”tax the resources of an already overburdened enforcement system and the public health system.”