In the US, investigators have discovered new anthrax traces in mailrooms at the Supreme Court, the State Department and possibly the Department of Health and Human Services.

Government officials reported three new incidents of anthrax in New Jersey and New York, bringing the number of confirmed cases in America to at least 15.

Authorities are on Tuesday awaiting confirmation of a preliminary diagnosis of inhalation anthrax for a critically ill hospital employee in New York City. Mayor Rudy Giuliani said at a late-night press conference Monday that the 61-year-old woman was in "very, very serious condition".