Anthrax chemical 'made in three countries'

Anthrax sent to the US Senate was reportedly treated with a chemical only three nations, including Iraq, are thought to be capable of making.

The spores in a letter sent to Tom Daschle, leader of the majority Democrats in the Senate, had been treated with the chemical to enable them to stay in the air.

This would make them easier to inhale and therefore deadlier it has been reported.

An official close to the investigation said only America, the Soviet Union and Iraq had been known to have developed the additives.

And there is hope that because each of the three countries used slightly different techniques, microscopic and chemical analysis might show up where the chemical was from.

But experts have warned it is unclear how secure the former Soviet Union's or Iraq's supplies are, and it is also possible their scientists could have defected elsewhere.

The revelation came as the FBI may be concentrating on home-grown terrorists, including right-wing extremists.

Investigators are looking at least 12 other letters sent to media outlets, which did not contain anthrax, but had similar messages and hand-writing as the letters laced with the deadly spores.

Hoax letters are also being investigated to see if some are from the same person or group.

Two letters sent to the media have also been discovered and FBI sources said their tone was far less menacing than the letter to Mr Daschle, which said: "You die now."