Anthrax spores were found at the remote military facility where all mail for the White House is screened. However, US officials are confident none found its way to the executive mansion, the White House said yesterday.
White House spokesman Mr Ari Fleischer said the remote site, which he did not identify, had been closed and all employees there were being tested for exposure to the potentially deadly bacteria, as were workers in the White House mailroom.
Anthrax-laced letters have been sent to the US Congress and to US media companies in New York and Florida over the past several weeks, leading to the deaths of three people and a nationwide scare about biological terrorism.
"This afternoon a positive anthrax culture was found at the remote mail site that serves the White House," Mr Fleischer told reporters. "Test results showed it to be positive for a small concentration of anthrax.
"The facility has been closed for further testing and decontamination. Tests will be performed on all mail received at this site to determine its source.
All employees at this site are being swabbed and tested," he said.
The White House has said that it suspects there is a link between the letters and the September 11th attacks.
Asked if anthrax had made its way to the White House, Mr Fleischer replied: "There have been a series of security precautions that have been put in place here at the White House, which give us high confidence that there is not an issue here at the White House itself."
The US Secret Service, which is responsible for the president's safety, said it did not know the origin of the anthrax spores but said the mail sent to the remote site comes through the Brentwood mail facility in Washington, DC, where two US postal workers died from anthrax this week.