Anthrax detected at US central bank

Anthrax killed five Americans last year

Anthrax spores have been detected at a facility handling mail for the US Federal Reserve.

"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 reserve said in a statement.

It is potentially a negative for the market because it could cast fear over the mail system

Stephen Massocca, stock market trader

The routine screening is held in a mobile trailer parked behind the buildings in central Washington.

However, a US official told Reuters news agency there was a "very good likelihood" that the traces could prove to be false readings or cross-contamination from earlier incidents.

White House spokesman Ari Fleischer said subsequent tests of the mailroom surfaces and mail distribution points within the buildings had all been negative.

Stocks hit

The positive anthrax test caused a stock market slump, reawakening fears that biological attacks could hit commerce and consumer confidence.

The Dow Jones industrial average fell 107.33 points, or 1.06%, to 10,034.50 on the news.

Stephen Massocca, head of trading at Pacific Growth Equities, said: "It is potentially a negative for the market because it could cast fear over the mail system. But you need to see more evidence of what is taking place here and how widespread it is."

Preliminary tests are often inaccurate and the swabs that produced the positive readings are being sent to a laboratory for additional testing. Results could take a week to come through.

A massive security operation was launched after last year's outbreaks

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

All mail addressed to the US Government is irradiated to kill anthrax, but even the presence of dead spores can produce an initial positive reading.

Federal Reserve spokesman David Skidmore said some of the mail was addressed to Chairman Alan Greenspan as well as other officials.

The last traces of anthrax in the US mail were found at the Federal Reserve in December. But they were believed to have been caused by cross-contamination and follow-up tests found no other positive results.

Five Americans died last year after envelopes containing anthrax spores were sent to the US Congress and prominent media figures.

At least 13 other people were infected but recovered.