The contaminated letter was postmarked Oct. 9 from Trenton, N.J., as was the one sent to Senate Majority Leader Tom Daschle, and contains similar handwriting, investigators said. One law-enforcement official said the return address - a fourth-grade class at a nonexistent school in New Jersey - also was the same.

Four people, including two Washington postal workers, have died from inhaled anthrax. But until Friday, only one letter carrying the germ inside the envelope had been found in Washington.

The letter was discovered Friday afternoon in a batch of segregated mail away from Congress, said Susan Neely, speaking for the Office of Homeland Security. She said the letter had not sickened anyone.

Investigators have said for weeks that there may be another anthrax-tainted letter. They have been hunting through unopened mail that has been under quarantine since postal workers were diagnosed with inhaled anthrax.

Although terrorism from abroad has not been ruled out, officials believe the anthrax attacks came from someone in the United States. However, they have not discovered the source of the letters. The second letter sent to a high-profile Democrat adds to the thin body of evidence.

``FBI and U.S. Postal Service investigators examining sequestered congressional mail have another letter which appears to contain anthrax,'' the FBI said in a statement Friday night.

The letter to Leahy, who is chairman of the Senate Judiciary Committee, ``appears in every respect to be similar to the other anthrax-laced letters,'' the FBI said.

It was located in one of more than 250 barrels of unopened mail sent to Capitol Hill and held since the discovery of an anthrax letter to Daschle on Oct. 15, the FBI said.

FBI Director Robert Mueller called the Vermont senator at his Washington-area home to tell him about the letter.

``I appreciate his call,'' Leahy said. ``This is a law enforcement matter and I will leave it to the proper authorities to report what they know and the procedures they are taking. I am confident they are taking the appropriate steps and that eventually they will find this person.''

Hazardous materials experts began sorting the quarantined congressional mail earlier this week at a facility in northern Virginia, the FBI said.

Preliminary tests were positive for anthrax from the letter, the FBI said. Further testing was being done.

Traces of anthrax have been found in about a dozen senators' offices in the Hart Senate Office Building across the street from the Capitol. That building remains closed for cleaning with chlorine dioxide gas.

Leahy's office is in a different building, but it's not clear where the letter was when mail deliveries to Congress ceased Oct. 15.

As a precaution, the Senate Russell and Dirksen buildings will be closed beginning Saturday to be tested for anthrax. A Capitol Police spokesman, Lt. Dan Nichols, said it was possible the Leahy letter was in one of those buildings before all undelivered mail to lawmakers was seized and taken away. Congress recessed Friday for Thanksgiving and will reconvene Nov. 27.

The most recent hot spots were in mailrooms at Howard University in Washington, in several more congressional offices and at the State Department's mail facility in Sterling, Va.

Three other letters with anthrax inside have been found, all of them bearing similarities. Letters to NBC News anchor Tom Brokaw and the New York Post appear to be photocopies. The third letter went to Daschle, D-S.D. All had block lettering and used the date style of 09-11-01.

Investigators also believe the anthrax in those three letters is the same Ames strain that is common to the United States. However, the anthrax in the newspaper's letter was in a heavier, grainier state and the material in Daschle's letter was light and buoyant.

The letter to Daschle contained about 2 grams of anthrax. If that were pure anthrax, one expert said that would amount to about 20 billion spores, or enough to sicken about 2 million people with the most deadly form of the disease.

A team worked Friday to decontaminate a postal distribution center in Raleigh, N.C., where a trace amount of anthrax was found on a shrink-wrapped pallet. The pallet had carried stamps from the Brentwood postal facility in Washington where two postal workers died.

Postal Service spokesman Bill Brown said the pallet had been in a vault at the Raleigh facility for about a month, meaning that anyone likely to be sickened by anthrax probably would have shown symptoms by now, and no one has.

In Boca Raton, Fla., where the anthrax attack first hit, testing found anthrax in more than 30 spots inside the American Media building. Health officials suggested there must have been more than one tainted letter sent to the tabloid publisher, although none has been found.

Fallout from the anthrax attacks continued. The government issued a detailed list of who must take antibiotics for a full 60 days. That includes about 5,000 people who may have been exposed to anthrax and could still get sick if they were to stop taking the medication.

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