No anthrax was detected at a government mail facility that handled a Federal Reserve letter that tested positive in preliminary readings, the Postal Service said Wednesday.

"All of our results are negative," said Thomas Day, vice president of engineering for the service.

The Washington postal facility was closed for the day while samples from the site were tested. It was expected to reopen Thursday.

Federal Reserve spokesman David Skidmore said a single letter addressed to Federal Reserve Vice Chairman Roger Ferguson had come back positive on Tuesday.

The suspect sample was sent to the Centers for Disease Control and Prevention for further testing. Late Wednesday, the Fed announced that those tests, conducted by the state of North Carolina under the CDC's guidance, found no presence of anthrax.

"The tests conducted today are considered to be definitive by CDC standards," the Fed said. The central bank also said the CDC in Atlanta planned more tests on the sample.

Since the anthrax-by-mail attacks in 2001, the Fed has been testing its mail in an outside trailer before allowing it into the central bank's headquarters. There had been positive readings twice before, in December 2001 and May 2002, but this was the first time that a more sophisticated laboratory test had detected the presence of live anthrax spores.

Five people died in the anthrax attacks in 2001, including two postal workers. Eighteen other people were infected.

Major mail sorting facilities in New Jersey and Washington were contaminated in the attacks and both remain closed. Fumigation to destroy the anthrax spores was recently completed at the Brentwood Road facility in Washington. Once further testing is completed, the New Jersey plant will be decontaminated.