Nearly 30 cases of anthrax exposure

Officials say the anthrax was refined for use as a weapon

In Washington, 29 people have tested positive for anthrax - increasing fears of new, full-blown cases of the potentially deadly disease.

There's no question that right now we are in a period of the unknown

Tommy Thompson
Health and Human Services Secretary

The people were workers in the office of Senate Majority leader Tom Daschle - who received a letter containing anthrax through the post.

It is impossible to know whether any of the latest group exposed to anthrax will develop the disease, and they are all being treated with antibiotics.

It was announced that the House of Representatives will close on Wednesday, as some staff in the office of another senator, Joseph Lieberman, were also reported to have tested positive for anthrax.

Workers at Mr Daschle's offices were tested for anthrax

US officials said on Wednesday that the form of anthrax found in Senator Daschle's letter appeared to be one of its most "potent" forms and most likely the work of experts.

Mr Daschle said FBI investigators had concluded that the anthrax strain was "a very potent form of anthrax that clearly was produced by someone who knew what he or she was doing".

US Government sources added that preliminary testing had indicated the contaminated powder to be refined enough to disperse easily through the air, increasing its potential as a deadly weapon.

The FBI has said that the handwriting was the same on the letter sent to Mr Daschle and another sent to NBC news anchor Tom Brokaw.

They both contained the messages "Death to America" and "God is great".

In other developments:

• US air strikes target Taleban front-line positions close to Kabul for the first time, according to the opposition Northern Alliance
• US Secretary of State Colin Powell receives strong support from Indian leaders during a whirlwind regional tour
• Northern Alliance fighters renew their efforts to capture the strategic town of Mazar-e-Sharif in northern Afghanistan, an opposition official says
• Confusion surrounds the whereabouts of Taleban Foreign Minister Mullah Abdul Wakil Muttawakil amid reports that he has left Afghanistan and made contact with former Afghan King Zahir Shah in Rome
• Taleban leader Mullah Omar sends a rallying radio message to his commanders, telling them God is on their side in a "holy war against infidels", according to AIP.
• Further sporadic fire is reported between Indian and Pakistani troops across the line of control in Kashmir as India says it will be "ruthless" with infiltrators
• Australia commits 1,500 troops and military hardware to be fully deployed by mid-November

Potential sources

Investigators say there are hints but no hard evidence as to where the anthrax could have come from.

Countries with stocks of weapon-grade anthrax

China

Iran

Iraq

Israel

Libya

North Korea

South Korea

Syria

Taiwan

Russia

However Michael Powers of the Chemical and Biological Arms Control Institute said that the sophistication of the strain found suggested "high level" involvement.

"Usually to produce that quality of anthrax requires a fairly high level of technological sophistication, which to my mind indicates some sort of state sponsorship," he said.

White House spokesperson Ari Fleischer said that the anthrax could not have come from America itself as US supplies of the bacteria were destroyed as part of the 1972 Biological Weapons Convention.

However at least ten other countries may have access to such biological agents, including Iraq and Iran.

Terrorists could also have obtained access to the bacteria via the many global laboratories that stock it for research purposes.

Fighting bioterrorism

Meanwhile, the newly-appointed US Homeland Security chief, Tom Ridge, has said fighting bioterrorism will be the main priority of the Bush administration in the coming weeks.

Interviewed by Mr Brokaw on America's NBC television network, Mr Ridge said there was not yet "credible evidence" to link the anthrax attacks to Saudi-born militant Osama Bin Laden, "but... we ought to operate under the presumption that it is".

He said the government was boosting its reserves of anthrax antibiotics and smallpox vaccine.

Earlier, FBI Director Robert Mueller said authorities had found no direct link with "organised terrorism" but had not ruled it out.

Hoaxers warned

The FBI says it has received more than 2,300 reports of suspected cases of anthrax since 1 October, including a spate of hoaxes.

Investigators found similarities in handwriting on the envelopes containing anthrax

US Attorney General John Ashcroft hit out at the perpetrators of phoney scares, warning culprits would be prosecuted.

"They create illegitimate alarm in a time of legitimate concern," he said.

In Florida, a 33-year-old Lee County Jail inmate faces up to 75 years in prison and a $50,000 fine after being charged with sending out letters claiming to contain anthrax spores.

Convicted robber Colin Perry is accused of writing five letters containing a white powdery substance and warning the recipients they were now infected by anthrax.

Strains of anthrax

Respiratory: Similar beginnings to flu but shock occurs between two and six days later - frequently fatal

Intestinal: Severe food poisoning type symptoms - up to 50% mortality

Cutaneous: Rarely painful skin lesion - fatal in one in 20 cases

Two men in Connecticut were also formally indicted on Tuesday on charges of making false anthrax threats.

CNN reported that Frederick Forcellina allegedly threatened to use a weapon of mass destruction in three Connecticut towns.

Earlier on Tuesday Mr Ashcroft said that another man, Joseph Faryniarz, was charged with making false statements connected to a scare in the state's Department of Health and Protection.