FBI fears 'inside job' on anthrax attacks

War on terrorism

US investigators searching for the source of the East Coast anthrax attacks are increasingly entertaining the theory that the culprit is a former member of the US biological weapons programme.

Federal agents have begun interrogating military officials linked to the old programme, which was phased out after 1969, and a number of government experts have been quoted in the media saying an "inside job" is a plausible, if explosive, explanation for the anthrax-laced letters that were sent to politicians and journalists in September and October.

"It's frightening to think that one of our own scientists could have done something like this, but it's definitely possible," one unnamed federal science adviser said in yesterday's New York Times. A source close to the investigation said it was "the most likely hypothesis".

This theory, echoed by a handful of academics attending the United Nations biological weapons conference in Geneva last week, has bitterly divided experts in the narrow fields of anthrax research and biological weapons inspection, however. Dr Richard Spertzl, a former weapons inspector in Iraq, said yesterday the insider job theory was scientifically dubious, unsupported by any evidence made public so far, and "terribly irresponsible".

"I think this is pure garbage," said the germ warfare specialist. "They're speaking out of ignorance, out of stupidity. They don't know anything about biological weapons or about the past US programme."

The US insider theory starts with the unanimously held premise that whoever sent the letters had access to a high-grade weapons laboratory and was familiar with techniques for weaponising deadly bacteria. According to military experts and government scientists cited by the New York Times, the letter sent to the Senate majority leader, Tom Daschle, contained an extraordinarily high concentration of anthrax – around one trillion spores per gram.

That is a far purer concentration than anything known to have been developed by a foreign government and is certainly out of the reach of an individual or individuals working alone. But it may, according to at least some experts, be consistent with weapons research conducted by the US more than 30 years ago.

One molecular biologist who attended the Geneva conference, Barbara Hatch Rosenberg, wrote a paper describing the letter-sender as "an American microbiologist who had, or once had, access to weaponised anthrax in a US government lab, or had been taught by a US defence expert how to make it". "Perhaps," she speculated in her paper, distributed by the Stockholm International Peace Research Institute, "he had a vial or two in his basement as a keepsake."

Dr Spertzl denounced this line as uninformed nonsense. The anthrax sent to Senator Daschle, he argued, had to come from either an active or recently active government laboratory. The US programme, he added, has been defunct for too long to be a plausible source. He is increasingly convinced the anthrax came from Iraq.

Dr Spertzl's rebuttal was partly substantiated by the senior research scientist at the army's biodefence laboratory in Fort Detrick, Maryland. Colonel Arthur Friedlander said the FBI had been asking questions about possible insider suspects but he said he thought this was unlikely. "We haven't had an offensive programme for a long time," he told the New York Times. "Nobody [at the army laboratory] has that kind of expertise."