Emerging evidence of the complex enhancement of anthrax used in one of the US attacks is narrowing the field of potential sources to state-sponsored labs in three countries, the US, the former Soviet Union and Iraq, reports here suggest.
Both the Washington Post and the New York Times quote scientists as saying that the anthrax used in the attack on the Capitol office of the Senate Majority Leader, Mr Tom Daschle, was treated to remove electrostatic charges allowing for much more efficient dispersal.
Questioned yesterday by journalists, the Director of Homeland Security, Mr Tom Ridge, would not confirm the reports, insisting that the tests necessary to do so were still incomplete. He did however confirm that the New York and Washington contaminated letters contained "indistinguishable strains" of the germ which had not been genetically manipulated. That sent to Mr Daschle was of a particularly fine form. Microscopic examination revealed that an as yet unidentified substance had been added to it.
The authorities have been sending mixed signals on whether that batch was "weaponised" or not, initially reporting that its extra infectivity was the product of special engineering, and then denying that it was any more than highly refined.
Now it appears, however, the anthrax's lethality had been enhanced with a technology only believed to be available to the US, the former Soviet Union, and Iraq.
One unconfirmed report suggested further tests had narrowed the source to the US. By coating the anthrax with a particular substance it was possible to remove the electrostatic charge on the microscopic particles, which otherwise have a tendency to cling together, allowing them to float and disperse more freely on the air. To turn the treated anthrax into a true weapon of mass destruction also requires techniques of mass production and efficient means of dissemination.
But Dr Bill Patrick, a key figure in the US's own biological warfare research, before President Richard Nixon renounced them in 1969, told the New York Times he had learned details of the federal inquiry from a senior investigator.
The Senate powder, Mr Patrick said, was quite potent and capable of travelling far through the air to hurt many people. He said the makers of the anthrax spores sent to Mr Daschle's office had produced a dry powder that was remarkably pure. A State Department mail handler was reported last night to have contracted anthrax. Meanwhile, in New York the discovery of contamination at the main postal sorting office has led to calls from postal workers' leaders for the testing of 5,000 workers on the premises.
Already some 10,000 people throughout the country are on precautionary courses of the drug cipro. Investigators say they have also detected anthrax in a new location in the same Senate office building where a contaminated letter arrived last week, raising new questions about how widely the germs were dispersed in the Capitol complex. The Secret Service is investigating two vials containing salmonella that were sent to former President Clinton's office in New York.
Meanwhile, briefing on the military campaign, in the face of complaints from a Northern Alliance figure that the US bombing has not been sufficiently vigorous, Gen Dick Myers, chairman of the Joint Chiefs, said they continued to bomb Taliban troop positions. He rejected suggestions that such bombing was "piecemeal".
Downing Street last night insisted it was "very sceptical" that terrorist mastermind Osama bin Laden could develop nuclear weapons after reports claimed he had acquired some of the necessary materials. Reports said he had acquired a key ingredient to make a nuclear weapon.