The team is more than triple the size of the force now searching for weapons and larger than was previously described. It will be headed by a two-star general in defense intelligence, the Pentagon said Wednesday.
Consisting of some 1,300 military and civilian experts in computers, intelligence, weapons, demolition and other matters, the group also will have former U.N. weapons inspectors and 800 support personnel.
They are joining 600 military and civilian experts from the armed forces, FBI, CIA, Defense Threat Reduction Agency and elsewhere who are already hunting for chemical, biological and nuclear weapons programs.
The Defense Department also confirmed it is investigating what officials said may be the most promising discovery so far — a trailer truck they say could turn out to be the first mobile biological lab recovered since the start of the war to disarm the government of Saddam Hussein.
The Bush administration alleged that Iraq had chemical, biological and nuclear weapons programs and said the main reason for the war was to destroy them. Despite weeks of searches at more than 100 sites, officials have reported finding nothing conclusive so far.
Officials said again Wednesday at a Pentagon news conference that finding the "smoking gun" will take time.
Asked if prewar intelligence was flawed, Defense Intelligence Agency Director Vice Adm. Lowell Jacoby said it was far too soon to tell.
"This is piecing together a major jigsaw puzzle, and we are only just beginning … to work the puzzle," Jacoby said.
On Wednesday, Lt. Gen. William Wallace, commander of the Army's V Corps, claimed his troops have "collected evidence, much of it documentary, that suggests there was an active program" for unconventional weapons.
Defense Undersecretary Stephen Cambone said the prewar lists of important sites to visit was about 1,000, including some 600 that related to weapons.
An additional 400 sites have been identified through Iraqi tips, documents and other leads since the war started.
Still, the searchers in Iraq have only explored 110 sites so far, Cambone said, 70 from the prewar list and 40 that emerged with new intelligence since the major fighting ended.
Several earlier possible finds have been proven false when more sophisticated analysis was conducted. Because field equipment is meant to protect troops from toxins, false positives are common in initial tests.
Some officials are starting to suggest there might not be any weapons, just the equipment needed to manufacture them, reports CBS News Correspondent David Martin.
They suspect Iraqi regime officials might have destroyed or moved the material from those sites. Top-level Iraqis in U.S. custody have so far maintained that Iraq had no illegal WMD programs, according to published reports.
Officials said the suspected biological lab was being tested by American forces in Iraq. The trailer matches the description of such laboratories given by various sources, including a defector who says he helped operate one.
Cambone said initial tests have been done on the trailer, which was taken into custody April 19 at a Kurdish checkpoint in northern Iraq. No biological agents have been found so far, but officials believe the trailer was washed with a caustic chemical to wipe away evidence. They said they may need to dismantle it to get to hard-to-reach surfaces.
The trailer, painted in a military color scheme, was found on a transporter normally used for tanks. It contains a fermenter and a system to capture exhaust gases, which an Iraqi defector said were parts of Iraq's mobile labs, Cambone said.
"While some of the equipment on the trailer could have been used for purposes other than biological weapons agent production, U.S. and U.K. technical experts have concluded that the unit does not appear to perform any function beyond what the defector said it was for, which is the production of biological agents," Cambone said.
Intelligence officials tell The Washington Post that even if the vehicle is a biological weapons lab, it is unclear if it was ever actually used to produce weapons and, if so, when.
In their work in Iraqi during the 1990s, United Nations inspectors heard reports that mobile labs existed but never found one.
Making the case for war to the U.N. Security Council, Secretary of State Colin Powell said in February that the U.S. knew of seven labs, perhaps comprising some 18 trucks that linked up in groups of two or three to form the labs. He claimed a lab could create anthrax and botulinum toxin.
The biological labs were part of a list of illegal arms the Bush administration accused Iraq of possessing.
Quoting U.N. reports, the president told Congress in January that Iraq had not disclosed the whereabouts of materials that could produce 25,000 liters of anthrax, more than 38,000 liters of botulinum toxin, 500 tons of sarin, mustard and VX nerve agent.
Although Pentagon officials suggested some Iraqi units were armed with chemical weapons just days before the war, none were found when those units were overrun, although protective suits and antidote injectors were found in some places.
Wallace speculated that the reason Saddam didn't use unconventional weapons against invading forces may be that these weapons were buried too well to retrieve before the fast coalition dash to Baghdad.
"Because they were so clever in disguising them and burying them so deep, they themselves had a problem getting to it," Wallace said.