BBCNews . 26 October
A series of cases have been linked to the mail
Anthrax found in a letter addressed to US Senate majority leader Tom Daschle may have been produced within the United States, the White House has said.
Spokesman Ari Fleischer said scientific advisers had concluded that "a PhD microbiologist in a sophisticated laboratory" could have been behind the outbreak.
But he added: "It does not rule out that it could be state supported, or that it comes from a foreign location."
His comments came after the Central Intelligence Agency reported that a trace amount of anthrax spores had been discovered at a mail handling building at its headquarters in suburban Virginia.
Bill Harlow, a CIA spokesman, said the anthrax at the agency's suburban Virginia headquarters was "medically insignificant", but the mail-handling building at the headquarters was closed for additional tests.
Friday also saw anthrax discovered on a filter removed from a warehouse that screens mail for the US Supreme Court in Washington. Federal officials said there was no evidence that spores were in the court building itself, although it was closed for testing.
The discoveries came a day after a State Department mail handler was taken to hospital with inhalation anthrax, the most serious form of the disease, and small amounts of anthrax bacteria were found at an army medical institute outside Washington.
They are the latest in a series of cases linked to the mail, which have prompted the US Postal Service to carry out checks on government-related mailrooms, hand out antibiotics to thousands of workers and purchase irradiation equipment to treat letters.
The US Postal Service cannot guarantee the safety of the mail
Two postal service workers, who were employed at the Washington sorting office that handled the letter sent to Senator Daschle died, earlier this week after contracting inhalation anthrax. Two of their colleagues are receiving treatment for the same form of the disease.
At present the only known source of anthrax in Washington is the letter sent to Senator Daschle. Investigators say either there are more undiscovered letters or anthrax spores are being spread through the postal system after being picked up by sorting machines.
In New York, anthrax has been detected on four mail-sorting machines at a processing station that handles millions of parcels a day.
Florida outbreak
In an earlier outbreak at a tabloid newspaper in Florida, two men contracted inhalation anthrax, one of whom died.
There have also been cases of cutaneous, or skin anthrax, a less serious form of the disease, in several New York media offices and mail offices in New Jersey. Seven people are known to have been infected with it.
So far, investigators have failed to trace the source of the anthrax or pinpoint a possible culprit, but identifying the method used to treat the spores may narrow the field.
Officials have no evidence of a link to those who planned the 11 September terror attacks on New York and Washington, but President George W Bush says he "wouldn't put it past" Saudi-born militant Osama Bin Laden, believed to have masterminded the attacks.