An artillery shell containing the deadly nerve agent sarin (search), found in the remains of a roadside bomb in Iraq, was made before the 1991 Gulf War (search), a senior military official said Wednesday.

Laboratory tests have confirmed that the chemical weapon sarin was in the remains of the bomb found in Baghdad on May 15, government officials said. The confirmation came at a U.S. lab that officials declined to identify.

At the Pentagon, Brig. Gen. David Rodriguez (search), deputy director of operations for the Joint Chiefs of Staff, said that the 155-millimeter artillery shell was made by the Iraqis before the 1991 Gulf War. The source of the bomb is still under investigation.

While its apparent age would mean it can't be regarded as evidence of recent Iraqi chemical weapons production, some analysts worry the shell may be part of a larger stockpile of Iraqi chemical weapons now in the hands of insurgents, but no more have turned up.

Defense Department spokesman Larry Di Rita told reporters, "It could be a lot more. It could be nothing. It's just too early to tell."

U.S. military officials also don't know whether the bombers were aware that they had a chemical weapon because the shell bore no labels to indicate it was anything except a normal explosive shell, the type used to make scores of roadside bombs in Iraq.

No one was injured after its initial detonation, but two American soldiers who removed the round had symptoms of low-level nerve agent exposure, officials have said.

A person exposed to a large dose of sarin can suffer convulsions, paralysis, loss of consciousness and could die from respiratory failure. But in small doses, people usually recover completely. Someone exposed to it may suffer runny nose and watery eyes, eye pain and blurred vision, drooling, rapid breathing and drowsiness. A lethal amount can be treated with the drug atropine.

The shell was a binary type, which has two chambers containing relatively safe chemicals until they are mixed. When the round is fired from an artillery gun, rotation of the shell mixes the chemicals to create sarin, which is supposed to disperse when it hits its target.

Because the shell was not fired from a gun but was detonated as a bomb, officials say the initial explosion on May 15 dispersed the precursor chemicals and apparently mixed them in only small amounts. In battle, such shells would have to be fired in great numbers to affect a large body of troops.

Iraq's first field-test of a binary-type shell containing sarin was in 1988, U.S. defense officials have noted. Saddam's government only disclosed that it was testing and producing sarin after Iraqi weapons chief Lt. Gen. Hussein Kamel al-Majid, Saddam's son-in-law, defected in 1995. But Iraq never declared any sarin or shells filled with sarin remained.

Saddam's alleged stockpile of weapons of mass destruction was the Bush administration's chief stated reason for invading Iraq, but U.S. weapons hunters have been unable to validate the prewar intelligence that described those stockpiles.

Some trace elements of mustard agent, an older type of chemical weapon, were detected in an artillery shell found in a Baghdad street this month, U.S. officials have said. They believe that shell also was from one of Saddam's old stockpiles.