Even amid the frenzy of journalists unearthing terrorist safe houses this week across the Afghan capital, this place is a little bit special.

Set behind high walls on Street 13 of the quiet Wazir Akbar Khan suburb, the house that was headquarters for a Pakistani-based relief organisation seems ordinary enough.

But inside is evidence that the Taliban were in the process of building - or at least trying to build - an anthrax bomb.

In an upstairs room is a make-shift workshop with rocket parts, solid fuel rods and tools scattered about.

On the floor are sheaves of documents downloaded from the Internet detailing the use of anthrax. They include details of the vaccination programme for the United States military.

And on the wall, a detailed diagram showing what appears to be an anthrax bomb set aloft in a helium-filled weather balloon.

The plan to spread the disease looks breathtakingly simple - strap a container with the disease underneath a converted rocket pod which is slung beneath a weather balloon. Send the balloon up, preferably over a sensitive site. Then watch as the US airforce does your work for you - shooting down the balloon and spreading the spores.

On a big wall chart the scheme is laid out, complete with an accurate rendition of a US F-16 fighter plane, a model of which also lies in the room, with the words "Your Days Are Limited - Bang," scrawled in English.

Also on the floor, among a jumble of Taliban propaganda newspapers in English and Dari, is a tape box with "Jihad" written next to a picture of a machine gun, and scribbled on the spine in Dari, the name Osama Bin Laden.

Downstairs by the French windows are two giant boxes containing black gas masks. By the door are two test tubes, sitting next to what looks like a stripped-down anti-tank shell.

Pakistanis with powerful Taliban connections lived here with their families, according to officials at the Save the Children headquarters next door.

"When the American bombing started, they moved the children out, right away," said an Afghan official at Save The Children. "A few men stayed on there. We didn't have contact with them. We are funded from America and they are from Pakistan, so we tried to keep out of their way." The house was taken from the owner, on pain of death, by the Taliban four years ago.

Since then it was used by members of the charity Ummah Tameer-e-Nau (UTN).

The charity president is Bashiruddin Mahmood, former head of research at the Pakistani Atomic Energy Authority, who was arrested by the Pakistani authorities very publicly last month and questioned about his links with the Taliban. Documents inside the house reveal that his charity, while doing nothing illegal, was certainly popular with the Taliban, funneling millions of dollars into schemes to rebuild roads and schools around the Taliban headquarters in Kandahar.

The charity board are well connected, including retired navy commanders and an airforce commodore from the Pakistani military.

One of the documents, again downloaded from the Internet, shows a picture of former US Defence Secretary William Cohen holding a 5 lb bag of sugar to show the amount of anthrax needed to wipe out half the population of Washington DC. A small bag of another white substance, tightly sealed, sits nearby.

This document, like all the others, is in English - the language of Pakistan - and was photocopied nine times. The evidence suggests this plan was laid out in a seminar. And the people who attended are presumably out there, somewhere, with this knowledge in their heads.

This is not the only house used for research into terror weapons. All across the city evidence is emerging that Kabul under the Taliban was a sort of MIT for terrorists.

All manner of schemes were worked on here - the city's Central Book Store reports doing a roaring trade in all kinds of technical manuals.

Everything from booby-traps to fertilizer bombs were being put together. The three neighbouring houses in this street, also occupied by Pakistani Taliban volunteers, have been stripped clean by their new owners in a hurry to move back, their secrets now lost.

Certainly, the contents of House 13 show the intention to launch a devastating biological attack, probably on the United States.

What it fails to show is whether the enthusiastic planners ever got beyond the boy-scout planning state of turning their idea into reality.

Acquiring weather balloons is not hard. Nor, in this part of the world, is finding rockets and bombs to attach to the bottom. But there is no evidence at all that the network got hold of the actual anthrax.

But that is not the point. The point of this discovery is that it was made by The Irish Times - not the West's intelligence services.

After the catastrophe of September 11th, America's mighty intelligence community admitted to a huge failure. And promised it would not happen again.

But two months later, what do we find? Kabul falls overnight, with the fleeing Taliban given no time to cover their tracks, and the first people to look around the next day are not spooks but journalists. It would have been simplicity itself for the intelligence experts to have asked the Northern Alliance to seal off the houses, while investigators got to work. Instead they are left open for journalists to sift through. The house on Street 13 is actually guarded by two soldiers who double as house-cleaners. They were busy disposing of all these documents when I arrived.

A chance will be missed. Probably most of the plans unearthed in these houses are amatuerish and will come to nothing. The intelligence services had better hope so, or else face the blame for a second colossal blunder.

On the face of it, a plan to spread anthrax over a US city from a second-hand weather balloon seems ridiculous. About as ridiculous, in fact, as the idea of hijackers armed with nothing more than penknives flying airliners into the World Trade Centre.