Health authorities said they were also awaiting test results on at least nine other people in the Washington area - not necessarily all postal employees - whose illnesses might also prove to be anthrax.
In announcing the new cases, Homeland Security Director Tom Ridge said the nation was fighting two fronts in the same war. "There's a battlefield outside this country and there's a ... battlefield inside this country," he said
Ever since a Florida tabloid newspaper company became the first target of an anthrax attack last month, a string of poisoned letters and traces of deadly powder have surfaced in New York, New Jersey and Washington. But investigators remained puzzled yesterday by the trail of contamination - from the letter mailed to Senate Majority Leader Tom Daschle or another still undiscovered - that has infected postal workers.
Mitchell Cohen of the Centers for Disease Control and Prevention acknowledged that he did not understand how the victims had inhaled anthrax because the letter to Daschle was taped shut. "This phenomenon ... is an evolution," he said. "How it's actually occurring isn't clear."
More than 2,200 employees at Brentwood central mail facility, about 15 blocks north of the Capitol, and at an express mail facility in Linthicum were urged to report for testing and to begin a 10-day course of antibiotics.
Both facilities have been closed for at least a week while investigators work to locate the source of the contamination.
Last night, the Centers for Disease Control and Prevention recommended that all workers in 36 local post offices that receive mail from the Brentwood station take antibiotics as a precaution. Officials said about 2,000 employees would be covered.
As hundreds of postal workers waited outside D.C. General Hospital for testing yesterday, some expressed anger that they went untested for anthrax exposure and remained on the job last week, even after Congressional staffers who might have been exposed were examined and sent home.
"We're the ones taking the risks, and no one has been telling us the truth about the danger we've been in," said Willard Tucker, 44, a letter carrier from Forestville. "If I'm infected, I'm already in trouble because they waited so long before we got tested."
In an effort to safeguard postal workers, Deborah Willhite, a Postal Service official, said yesterday that the CDC and other health authorities had reversed their previous position and now advised that postal workers be furnished with gloves and masks.
Postmaster General John E. Potter said the Postal Service also was increasing security at its facilities and would introduce ultraviolet technology to sanitize mail. He also said that post offices had halted cleaning their machinery with blowers, which could possibly circulate anthrax spores.
The Brentwood mail center was targeted by investigators because they believe an anthrax-laced letter mailed from New Jersey on Oct. 9 and addressed to Daschle passed through the facility en route to Capitol Hill.
The Linthicum express mail facility near Baltimore-Washington International Airport was closed after Leroy Richmond, 57, a postal employee who worked there and at Brentwood, became sick during the weekend with the inhaled form of anthrax.
Ridge defended the actions of the Centers for Disease Control and others agencies yesterday. He said it took investigators a while to "follow the chain" of the Daschle letter back to Brentwood and determine there might be a problem at the facility.
"I think they moved quickly, as quickly as they could," Ridge said.
Cohen said that, much like the D.C. incident, previous investigations in Florida and New York, where anthrax-tainted letters also turned up, did not initially show anthrax in postal offices.
Spores have now turned up at a regional facility in Trenton, three post offices in South Florida and at a postal substation in Washington, as well as mailrooms in several House and Senate office buildings.