Trailer found in Iraq 'was bioweapons lab'

American and British experts have concluded that a trailer found by Allied forces three weeks ago in northern Iraq was a mobile bioweapons laboratory, a senior Pentagon official said yesterday.

"They have not found another plausible use for it," Stephen Cambone, under secretary of defence for intelligence said, confirming what appears to be the first real breakthrough in the search for Saddam Hussein's alleged, but elusive, chemical, germ, and nuclear weapons programmes.

He declined to describe the find as a "smoking gun," saying substantial further testing was needed. But the trailer was painted in military colours, on a carrier normally used for transporting tanks, while its gas recovery systems were "not necessary for legitimate biological work", Mr Cambone said.

The trailer is like the one outlined in the 5 February presentation to the UN Security Council by Colin Powell when the Secretary of State presented evidence suggesting that Baghdad had several such laboratories. The information at that time, American officials claimed, had come from a source who had helped to design the facility.

The discovery, if true, will be a relief to the Bush administration, which has come under increasing pressure not only abroad but also in the press at home and on Capitol Hill to produce proof of the unconventional weapons programmes whose existence was the very reason that was advanced for the Anglo-American invasion.

In the run-up to the war, American and British leaders claimed Saddam had chemical weapons ready for battlefield deployment in 45 minutes, and had stocks of biological arms, while Dick Cheney, the Vice-President, said Saddam had "reconstituted" his nuclear weapons programme. Later many of the important documents supporting the nuclear allegations were revealed as blatant forgeries.

Hours before Mr Cambone spoke, the White House spokes-man Ari Fleischer came under sustained questioning about the failure thus far to unearth such weapons for the first time. Mr Fleischer insisted they did exist and would be discovered in due course.

Mr Cambone said that of the list of 580 suspected sites American investigators had taken with them into Iraq, 70 had been inspected, as well as 40 other possible sites of which the US had not been aware before the war. By the end of May, some 2,000 experts would be engaged in trying to "unravel the mystery of Iraq's WMD".

The alleged mobile laboratory was discovered on 19 April at Tall-Kayf, near Mosul. It contained fermenting devices of the type used to make germ weapons but had been cleaned with a caustic material such as ammonia or bleach.

The find "has confirmed what our sources said existed. I'm sure we will discover WMD programmes as varied and extensive as the Secretary of State suggested [at the UN]."

Earlier, General William Wallace, the commander of US ground forces during the war, speculated that he thought Saddam did not use unconventional weapons against invading forces because they were too well hidden to retrieve before the fast coalition dash to Baghdad.

General Wallace attracted controversy early in the conflict when he said the unexpectedly strong resistance from Iraqi Fedayeen guerrillas was "not what we had war-gamed for." He was rebuked for that by Donald Rumsfeld, the Secretary of Defence, and is being moved to another job.