From the Washington Post:

"Within the first four hours," said one team member, "it was clear to everyone that these were not biological labs." News of the team's early impressions leaped across the Atlantic well ahead of the technical report. Over the next two days, a stream of anxious e-mails and phone calls from Washington pressed for details and clarifications. The reason for the nervousness was soon obvious: In Washington, a CIA analyst had written a draft white paper on the trailers, an official assessment that would also reflect the views of the DIA. The white paper described the trailers as "the strongest evidence to date that Iraq was hiding a biological warfare program." It also explicitly rejected an explanation by Iraqi officials, described in a New York Times article a few days earlier, that the trailers might be mobile units for producing hydrogen. But the technical team's preliminary report, written in a tent in Baghdad and approved by each team member, reached a conclusion opposite from that of the white paper. On May 29, 2003, 50 days after the fall of Baghdad, President Bush proclaimed a fresh victory for his administration in Iraq: Two small trailers captured by U.S. and Kurdish troops had turned out to be long-sought mobile "biological laboratories." He declared, "We have found the weapons of mass destruction."

The claim, repeated by top administration officials for months afterward, was hailed at the time as a vindication of the decision to go to war. But even as Bush spoke, U.S. intelligence officials possessed powerful evidence that it was not true.

A secret fact-finding mission to Iraq -- not made public until now -- had already concluded that the trailers had nothing to do with biological weapons. Leaders of the Pentagon-sponsored mission transmitted their unanimous findings to Washington in a field report on May 27, 2003, two days before the president's statement.

The three-page field report and a 122-page final report three weeks later were stamped "secret" and shelved. Meanwhile, for nearly a year, administration and intelligence officials continued to publicly assert that the trailers were weapons factories.

The authors of the reports were nine U.S. and British civilian experts -- scientists and engineers with extensive experience in all the technical fields involved in making bioweapons -- who were dispatched to Baghdad by the Defense Intelligence Agency for an analysis of the trailers. Their actions and findings were described to a Washington Post reporter in interviews with six government officials and weapons experts who participated in the mission or had direct knowledge of it.

None would consent to being identified by name because of fear that their jobs would be jeopardized. Their accounts were verified by other current and former government officials knowledgeable about the mission. The contents of the final report, "Final Technical Engineering Exploitation Report on Iraqi Suspected Biological Weapons-Associated Trailers," remain classified. But interviews reveal that the technical team was unequivocal in its conclusion that the trailers were not intended to manufacture biological weapons. Those interviewed took care not to discuss the classified portions of their work.

"There was no connection to anything biological," said one expert who studied the trailers. Another recalled an epithet that came to be associated with the trailers: "the biggest sand toilets in the world."

The story of the technical team and its reports adds a new dimension to the debate over the U.S. government's handling of intelligence related to banned Iraqi weapons programs. The trailers -- along with aluminum tubes acquired by Iraq for what was claimed to be a nuclear weapons program -- were primary pieces of evidence offered by the Bush administration before the war to support its contention that Iraq was making weapons of mass destruction.

Intelligence officials and the White House have repeatedly denied allegations that intelligence was hyped or manipulated in the run-up to the U.S.-led invasion of Iraq in March 2003. But officials familiar with the technical team's reports are questioning anew whether intelligence agencies played down or dismissed postwar evidence that contradicted the administration's public views about Iraq's weapons of mass destruction. Last year, a presidential commission on intelligence failures criticized U.S. spy agencies for discounting evidence that contradicted the official line about banned weapons in Iraq, both before and after the invasion.

Spokesmen for the CIA and the Defense Intelligence Agency declined to comment on the specific findings of the technical report because it remains classified. A spokesman for the DIA asserted that the team's findings were neither ignored nor suppressed, but were incorporated in the work of the Iraqi Survey Group, which led the official search for Iraqi weapons of mass destruction. The survey group's final report in September 2004 -- 15 months after the technical report was written -- said the trailers were "impractical" for biological weapons production and were "almost certainly intended" for manufacturing hydrogen for weather balloons.

"Whether the information was offered to others in the political realm I cannot say," said the DIA official, who spoke on the condition that he not be identified.

Intelligence analysts involved in high-level discussions about the trailers noted that the technical team was among several groups that analyzed the suspected mobile labs throughout the spring and summer of 2003. Two teams of military experts who viewed the trailers soon after their discovery concluded that the facilities were weapons labs, a finding that strongly influenced views of intelligence officials in Washington, the analysts said. "It was hotly debated, and there were experts making arguments on both sides," said one former senior official who spoke on the condition that he not be identified.

The technical team's findings had no apparent impact on the intelligence agencies' public statements on the trailers. A day after the team's report was transmitted to Washington -- May 28, 2003 -- the CIA publicly released its first formal assessment of the trailers, reflecting the views of its Washington analysts. That white paper, which also bore the DIA seal, contended that U.S. officials were "confident" that the trailers were used for "mobile biological weapons production."

Throughout the summer and fall of 2003, the trailers became simply "mobile biological laboratories" in speeches and press statements by administration officials. In late June, Secretary of State Colin L. Powell declared that the "confidence level is increasing" that the trailers were intended for biowarfare. In September, Vice President Cheney pronounced the trailers to be "mobile biological facilities," and said they could have been used to produce anthrax or smallpox.

By autumn, leaders of the Iraqi Survey Group were publicly expressing doubts about the trailers in news reports. David Kay, the group's first leader, told Congress on Oct. 2 that he had found no banned weapons in Iraq and was unable to verify the claim that the disputed trailers were weapons labs. Still, as late as February 2004, then-CIA Director George J. Tenet continued to assert that the mobile-labs theory remained plausible. Although there was "no consensus" among intelligence officials, the trailers "could be made to work" as weapons labs, he said in a speech Feb. 5.

Tenet, now a faculty member at Georgetown's Edmund A. Walsh School of Foreign Service, declined to comment for this story.

Kay, in an interview, said senior CIA officials had advised him upon accepting the survey group's leadership in June 2003 that some experts in the DIA were "backsliding" on whether the trailers were weapons labs. But Kay said he was not apprised of the technical team's findings until late 2003, near the end of his time as the group's leader.

"If I had known that we had such a team in Iraq," Kay said, "I would certainly have given their findings more weight."

Even before the trailers were seized in spring 2003, the mobile labs had achieved mythic stature. As early as the mid-1990s, weapons inspectors from the United Nations chased phantom mobile labs that were said to be mounted on trucks or rail cars, churning out tons of anthrax by night and moving to new locations each day. No such labs were found, but many officials believed the stories, thanks in large part to elaborate tales told by Iraqi defectors.

The CIA's star informant, an Iraqi with the code name Curveball, was a self-proclaimed chemical engineer who defected to Germany in 1999 and requested asylum. For four years, the Baghdad native passed secrets about alleged Iraqi banned weapons to the CIA indirectly, through Germany's intelligence service. Curveball provided descriptions of mobile labs and said he had supervised work in one of them. He even described a catastrophic 1998 accident in one lab that left 12 Iraqis dead.

Curveball's detailed descriptions -- which were officially discredited in 2004 -- helped CIA artists create color diagrams of the labs, which Powell later used to argue the case for military intervention in Iraq before the U.N. Security Council.

"We have firsthand descriptions of biological weapons factories on wheels and on rails," Powell said in the Feb. 5, 2003, speech. Thanks to those descriptions, he said, "We know what the fermenters look like. We know what the tanks, pumps, compressors and other parts look like."

The trailers discovered in the Iraqi desert resembled the drawings well enough, at least from a distance. One of them, a flatbed trailer covered by tarps, was found in April by Kurdish fighters near the northern city of Irbil. The second was captured by U.S. forces near Mosul. Both were painted military green and outfitted with a suspicious array of gear: large metal tanks, motors, compressors, pipes and valves.

Photos of the trailers were quickly circulated, and many weapons experts were convinced that the long-sought mobile labs had been found.

Yet reaction from Iraqi sources was troublingly inconsistent. Curveball, shown photos of the trailers, confirmed they were mobile labs and even pointed out key features. But other Iraqi informants in internal reports disputed Curveball's story and claimed the trailers had a benign purpose: producing hydrogen for weather balloons.

Back at the Pentagon, DIA officials attempted a quick resolution of the dispute. The task fell to the "Jefferson Project," a DIA-led initiative made up of government and civilian technical experts who specialize in analyzing and countering biological threats. Project leaders put together a team of volunteers, eight Americans and a Briton, each with at least a decade of experience in one of the essential technical skills needed for bioweapons production. All were nongovernment employees working for defense contractors or the Energy Department's national labs.

The technical team was assembled in Kuwait and then flown to Baghdad to begin their work early on May 25, 2003. By that date, the two trailers had been moved to a military base on the grounds of one of deposed president Saddam Hussein's Baghdad palaces. When members of the technical team arrived, they found the trailers parked in an open lot, covered with camouflage netting.

The technical team went to work under a blistering sun in 110-degree temperatures. Using tools from home, they peered into vats, turned valves, tapped gauges and measured pipes. They reconstructed a flow-path through feed tanks and reactor vessels, past cooling chambers and drain valves, and into discharge tanks and exhaust pipes. They took hundreds of photographs.

By the end of their first day, team members still had differing views about what the trailers were. But they agreed about what the trailers were not.

"Within the first four hours," said one team member, who like the others spoke on the condition he not be named, "it was clear to everyone that these were not biological labs."

News of the team's early impressions leaped across the Atlantic well ahead of the technical report. Over the next two days, a stream of anxious e-mails and phone calls from Washington pressed for details and clarifications.

The reason for the nervousness was soon obvious: In Washington, a CIA analyst had written a draft white paper on the trailers, an official assessment that would also reflect the views of the DIA. The white paper described the trailers as "the strongest evidence to date that Iraq was hiding a biological warfare program." It also explicitly rejected an explanation by Iraqi officials, described in a New York Times article a few days earlier, that the trailers might be mobile units for producing hydrogen.

But the technical team's preliminary report, written in a tent in Baghdad and approved by each team member, reached a conclusion opposite from that of the white paper.

Team members and other sources intimately familiar with the mission declined to discuss technical details of the team's findings because the report remains classified. But they cited the Iraqi Survey Group's nonclassified, final report to Congress in September 2004 as reflecting the same conclusions.

That report said the trailers were "impractical for biological agent production," lacking 11 components that would be crucial for making bioweapons. Instead, the trailers were "almost certainly designed and built for the generation of hydrogen," the survey group reported.

The group's report and members of the technical team also dismissed the notion that the trailers could be easily modified to produce weapons.

"It would be easier to start all over with just a bucket," said Rod Barton, an Australian biological weapons expert and former member of the survey group.

The technical team's preliminary report was transmitted in the early hours of May 27, just before its members began boarding planes to return home. Within 24 hours, the CIA published its white paper, "Iraqi Mobile Biological Warfare Agent Production Plants," on its Web site.

After team members returned to Washington, they began work on a final report. At several points, members were questioned about revising their conclusions, according to sources knowledgeable about the conversations. The questioners generally wanted to know the same thing: Could the report's conclusions be softened, to leave open a possibility that the trailers might have been intended for weapons?

In the end, the final report -- 19 pages plus a 103-page appendix -- remained unequivocal in declaring the trailers unsuitable for weapons production.

"It was very assertive," said one weapons expert familiar with the report's contents.

Then, their mission completed, the team members returned to their jobs and watched as their work appeared to vanish.

"I went home and fully expected that our findings would be publicly stated," one member recalled. "It never happened. And I just had to live with it."