WASHINGTON — An artillery shell rigged to explode in a roadside bomb in Baghdad instead dispersed a tiny amount of sarin, a nerve gas that Saddam Hussein produced in the 1980s, U.S. officials said Monday.
Officials cautioned that field tests had identified traces of sarin but that more sophisticated tests would be conducted outside Iraq. During the invasion of Iraq last year, U.S. forces reported many discoveries of poison gases or germ weapons, but further testing showed all to be false alarms.
The Bush administration justified going to war in Iraq chiefly because of concerns that Hussein's regime was producing and stockpiling sarin and other banned weapons in violation of U.N. resolutions. No illicit stockpiles, nor programs to produce them, have been found since the invasion 14 months ago.
Brig. Gen. Mark Kimmitt, the chief U.S. military spokesman in Iraq, said during a news conference in Baghdad that a U.S. convoy found the 155-millimeter shell rigged to explode along a road several days ago but the device detonated before soldiers could disable it. He said field tests showed "very, very small traces" of sarin.
Kimmitt said he did not believe that the insurgents who planted the bomb knew that the shell contained chemicals rather than explosives. The specially designed "binary" shell is designed to mix chemicals from separate chambers, producing a lethal gas, only after it is fired.
Exploding the shell on the road, he said, is "virtually ineffective as a chemical weapon." He added, "It just blows up and you have chemicals spewing out -- minor amounts going in different directions. It's ineffective."
Kimmitt said two soldiers who transported the material were treated for minor exposure to chemical agents and released. The area "is not a continuing threat" and "needs no special marking off [or] decontamination," he added.
Kimmitt said the chemical munition appeared to be left over from the 1980s, when Baghdad secretly produced hundreds of tons of poison gas. United Nations records show that the sarin Iraq produced in the mid-1980s degraded quickly, however, and was no longer lethal by the early 1990s.
Still, if sarin is confirmed, officials said, Pentagon planners must consider the possibility that Iraqi insurgents have access to other chemical weapons and will seek to use them against U.S. forces. Unless treated quickly with antidotes, sarin that has not degraded can cause death.
"What is of concern is that there may be more of them out there," said a U.S. official, who requested anonymity.
Hussein's regime insisted before the war that it no longer had chemical weapons. Most Western intelligence agencies were convinced that Baghdad retained at least some leftover supplies from the 1980s, and U.S. intelligence officials argued that Baghdad had secretly produced hundreds of tons more in recent years.
Defense Secretary Donald H. Rumsfeld said the initial field tests were "not perfect," and he called for caution.
"We have to be careful," Rumsfeld told reporters after a speech to the Heritage Foundation, a Washington think tank. "We can't take something that's inaccurate."
If sarin is confirmed, Rumsfeld said, weapons experts will seek to determine where the shell is from, how it came to be used in a roadside bomb "and what might it mean in terms of the risks to our forces."
The Bush administration was embarrassed last year when U.S. intelligence agencies publicly claimed that they had found two Iraqi trucks designed to produce germ weapons. But experts quickly challenged those claims, and the CIA recently backed away from its assertions.
Times staff writer Alissa J. Rubin in Baghdad contributed to this report.