Anthrax found in Federal Reserve mail

The US Federal Reserve says it has found traces of anthrax on 20 pieces of mail.

"Routine preliminary tests, administered late Tuesday and Wednesday by board and contract employees wearing protective environmental suits, detected anthrax spores in small batches of mail totalling about 20 pieces," the Fed said in a statement.

The routine screening is held in a mobile trailer parked behind the Federal Reserve's main buildings in downtown Washington.

Such preliminary tests are often inaccurate and further tests are being conducted.

"The affected mail was routine commercial and business mail and did not have any of the characteristics identified by the FBI as suspicious," the statement said.

If further testing shows that the letters are indeed infected, it will be the second time the central bank is exposed to the deadly bacteria, which killed five Americans last year.