Anthrax shuts down US legislature

America's House of Representatives was today being closed after 29 workers tested positive for anthrax exposure and spores were found in a ventilation system.

Members were due to finish business early tonight to allow the Capitol and all its offices to be shut down to allow public health officials to search for more anthrax spores.

Some have been found in ventilation systems after a letter addressed to Tom Daschle, the leader of the majority Democrats in the Senate, was found to contain anthrax.

At least 29 people, including members of Mr Daschle's staff and two Capitol Police officers, tested positive for exposure to the potentially-deadly spores.

Two hundred more people, including senior Congress members, were prescribed antibiotics as a preventative measure, while senior Senate leaders were in talks to decide whether to close the upper house of the American Congress.

Dennis Haster, speaker of the House of Representatives, said: "It has got through the ventilation system. It was also found in the mail room of the Senate.

"We do not know what has come through our postal machines. We do not know what has been distributed.

"We think it is prudent to take some time to go through and make sure this building is environmentally safe."

The exposures are the latest in a series of incidents involving the spores, which can lead to a fatal infection of the respiratory system.

The workers were staff working for Mr Daschle and who were in his office when a letter addressed to him was opened and found to contain anthrax.

Today all were receiving antibiotics, while more than 200 people who work in Congress, including some of its most senior politicians, are taking the drugs as a preventative measure.

Hundreds more were waiting for tests for exposure to the infection, fearing that the spores could have got into the building where Mr Daschle's office is located when the letter was opened.

Mr Daschle had earlier said that the type of spores found in the letter addressed to him were "a very potent form of anthrax".

"We were told that it was a very strong form of anthrax, a very potent form of anthrax that clearly was produced by somebody who knew what he or she was doing."