Before the war, the Bush administration pressured U.N. inspectors to question reluctant Iraqi scientists as part of the hunt for unconventional weapons.
Once Saddam Hussein was removed, U.S. officials expected the scientists and others would feel free to reveal secrets about Iraq's suspected hidden arsenal.
But few have come forward. And U.S. officials say those in custody are sticking to their stories -- that Iraq hasn't had chemical, biological or nuclear weapons programs in years.
While the major combat has ended, one of the war's main goals -- disarming Iraq of any weapons of mass destruction -- has yet to be achieved.
A military official involved with a small group of U.S.-led search teams in Iraq said they were under "intense pressure from Washington to come up with something." The official, who spoke on condition of anonymity, said the teams were overwhelmed with work and looking forward to planned reinforcements.
The teams are visiting suspect sites and testing for the presence of any weapons or indications that ingredients may have been destroyed there. Some are sifting through documents and intelligence reports for clues.
But those involved in what is known as "site exploitation," aren't interviewing the hundreds of Iraqi scientists whom U.S. officials have said would be the key to finding any banned weapons.
Two experts involved in the planning for the weapons hunt said a handful of top scientists already in U.S. custody were being questioned by intelligence officials, not by weapons experts or interrogators with strong scientific backgrounds.
Some senior working-level scientists and researchers have been interviewed by reporters in their Baghdad homes or at their offices. But few, if any, have been visited by Americans.
One reason may be that the current search teams are limited in their mission, expertise and staff, forcing them to wait for scientists to volunteer information rather than seeking them out.
In an effort to reach the larger scientific community, coalition radio in Iraq called on Iraqi scientists and engineers to come forward with any details that could prove useful.
"Anyone who provides information regarding weapons programs will be treated with respect and dignity to ensure Iraq's complete and comprehensive disarmament."
There is concern that some scientists are afraid to speak out.
"People we've heard from are scared of a situation like Guantanamo Bay" -- that they will be imprisoned under austere conditions like those faced by terror suspects captured in Afghanistan, said Corey Hinderstein, senior analyst at the Washington-based Institute for Science and International Security.
U.S.: Prisoners lying
U.S. officials said this week that senior figures in custody -- including Amer al-Saadi, Saddam's alleged point man on chemical and biological agents; Amer Rashid, Iraq's oil minister and a top missile expert and Jaffer Jaffer, the father of Iraq's former nuclear weapons program -- denied Iraq had any unconventional weapons in recent years.
The officials said they believed many of the prisoners were lying to protect themselves. Some may be trying to cut deals before agreeing to reveal information.
There has been discussion in the Bush administration and among disarmament experts about what to do with the scientists. Some feel that those who served at the top could be prosecuted for war crimes, but many believe the vast majority should be reintegrated into society and even prevented from leaving Iraq.
"They could work for other proliferators or terrorist groups if they're allowed to leave," said Jonathan Tucker, a former U.N. inspector and a bioweapons expert now at the U.S. Institute for Peace.
Tucker and others said it was imperative that those involved in the weapons search started looking immediately for scientists who are known to have been involved in programs in the past.
"The U.S. made such an important point of getting the U.N. to talk to the scientists, and the fact that we seem, in a certain sense, not to be following our own advice is perplexing," said Matthew Bunn, a nuclear expert at Harvard.
Search efforts increased
The government is in the process of beefing up the weapons search and plans to send in more than 1,000 people from the military and civilian sectors to help analyze new information, interrogate prisoners and scour suspicious sites. Known as the Iraq Survey Group, they will take control of the roughly 200 experts already on the ground.
But thus far, some of the former inspectors have said the U.S. teams are too small and lack sufficient expertise and equipment.
In November, it took U.N. inspectors only two weeks to be fully operational in Iraq and within days they were conducting multiple searches across the country. With more than 100 inspectors working at any given time, the U.N. teams were conducting up to 20 inspections a day by January.
United Nations inspectors were also better equipped, with their own helicopters, a fleet of vehicles and extensive onsite laboratories.
Still, they were unable to find any evidence to support the administration's claim that Iraq was concealing weapons. As it became clear they weren't finding the weapons the administration said were there, France suggested beefing up the teams but the United States opposed it.
U.S. officials now say the weapons are either well hidden or were destroyed in the run-up to the war. There is no firm evidence they were moved to other countries, they say.