Tests on an artillery shell that blew up in Iraq on Saturday confirm that it did contain an estimated three or four liters of the deadly nerve agent sarin (search), Defense Department officials told Fox News Tuesday.

The artillery shell was being used as an improvised roadside bomb, the U.S. military said Monday. The 155-mm shell exploded before it could be rendered inoperable, and two U.S. soldiers were treated for minor exposure to the nerve agent.

Three liters is about three-quarters of a gallon; four liters is a little more than a gallon.

"A little drop on your skin will kill you" in the binary form, said Ret. Air Force Col. Randall Larsen, founder of Homeland Security Associates. "So for those in immediate proximity, three liters is a lot," but he added that from a military standpoint, a barrage of shells with that much sarin in them would more likely be used as a weapon than one single shell.

The soldiers displayed "classic" symptoms of sarin exposure, most notably dilated pupils and nausea, officials said. The symptoms ran their course fairly quickly, however, and as of Tuesday the two had returned to duty.

The munition found was a binary chemical shell, meaning it featured two chambers, each containing separate chemical compounds. Upon impact with the ground after the shell is fired, the barrier between the chambers is broken, the chemicals mix and sarin is created and dispersed.

Intelligence officials stressed that the compounds did not mix effectively on Saturday. Due to the detonation, burn-off and resulting spillage, it was not clear exactly how much harmful material was inside the shell.

A 155-mm shell can hold two to five liters of sarin; three to four liters is likely the right number, intelligence officials said.

Another shell filled with mustard gas (search), possibly also part of an improvised explosive device (IED) was discovered on May 2, Defense Dept. officials said.

The second shell was found by passing soldiers in a median on a thoroughfare west of Baghdad. It probably was simply left there by someone, officials said, and it was unclear whether it was meant to be used as a bomb.

Click Here to Read the Weapons of Mass Destruction Handbook

Testing done by the Iraqi Survey Group (search) — a U.S.-organized group of weapons inspectors who have been searching for weapons of mass destruction (search) since the ouster of Saddam Hussein — concluded that the mustard gas was "stored improperly" and was thus "ineffective."

"It's not out of the ordinary or unusual that you would find something [like these weapons] in a haphazard fashion" in Iraq, Edward Turzanski, a political and national security analyst, told Fox News on Tuesday.

But "you have to be very careful not to be entirely dismissive of it," he added. "It remains to be seen whether they have more shells like this."

Iraq: A 'Bazaar of Weapons'

New weapons caches are being found every day, experts said, including "hundreds of thousands" of rocket-propelled grenades and portable anti-aircraft weapons.

"Clearly, if we're gonna find one or two of these every so often — used as an IED or some other way — the threat is not all that high, but it does confirm suspicion that he [Saddam] did have this stuff," said Ret. U.S. Army Col. Robert Maginnis.

"It is a bazaar of weapons that are available on every marketplace throughout that country," Maginnis added. "We're doing everything we can to aggressively disarm these people, but there were so many things that were stored away by Saddam Hussein in that country ... it's a huge job that we're tackling."

Some experts were concerned that enemy fighters with access to potential weapons of mass destruction in a country full of stockpiles could mean more risk to coalition forces and Iraqis.

"What we don't know is if there are other shells, which there certainly could be," said Dennis Ross, a former ambassador and special Middle East coordinator and a Fox News foreign affairs analyst. "We also don't know whether or not these kind of shells could be used as explosives, which could have a more devastating effect on our troops."

Other experts said the individual shells themselves don't pose a threat to the masses.

"I'm not as concerned they're going to use a lot of chemical munitions," Maginnis said. "They're not gonna use these as improvised explosive devices because they don't have a big blast associated with them, but they do combine those two compounds into the noxious sarin gas. But they can't do it all that well with a small explosive charge."

"The reality is, they'd have to have a whole bunch of these things," he added, "have to find some way of blowing them with a large charge to even create a cloud."

That doesn't mean insurgents couldn't find a better way to make the devices to create a more "terrorist-type of attack" against U.S. forces, Maginnis continued.

The task of military analysts in Baghdad will be to determine how old the sarin shell is. A final determination will have a significant effect on how weapons researchers and inspectors proceed.

Some experts suggested that the two shells, which were unmarked, date back to the first Persian Gulf War. The mustard gas shell may have been one of 550 projectiles that Saddam failed to account for in his weapons declaration shortly before Operation Iraqi Freedom began. Iraq also failed to account for 450 aerial bombs containing mustard gas.

It's not clear if enemy fighters simply found an old stockpile of weapons, or if they even knew what was inside.

Defense Secretary Donald Rumsfeld reacted cautiously to the news of the discoveries.

"What we have to then do is to try to track down and figure out how it might be there, what caused that to be there in this improvised explosive device, and what might it mean in terms of the risks to our forces," Rumsfeld said Monday.

Kurds: We Have Evidence of WMD

An Iraqi Kurdish official had no doubt similar substances will be found as the weapons hunt continues.

"We don't know where they are, but we suspect they are hidden in many locations in Iraq," Howar Ziad, the Kurdish representative to the United Nations, told Fox News on Tuesday. "It's quite possible that even the neighboring states who are against the reform of Iraq ... are helping the Saddamites in hiding."

"As we know, the Baathist regime had a track record of using" these chemicals against people in Iraq, such as the Kurds, Ziad continued. "He's [Saddam] never kept any commitment he's ever made to the international committee nor to the people" to not use such deadly materials.

Saddam's regime used sarin in mass amounts during an air attack on the Kurdish town of Halabja (search) in 1988, toward the end of the Iran-Iraq War. More than 5,000 people are believed to have died in Halabja and surrounding villages, with more than 65,000 were injured.

Both Iraq and Iran used chemical weapons during the 1980-88 war.

Ziad said the United Nations, the World Health Organization and others had not "bothered" to travel to the Iraqi Kurdistan to see the firsthand effects sarin and other chemical weapons had on people and to get proof that Saddam did in fact possess such weapons.

"We have evidence — we have victims of the use of those agents, and we're still waiting for WHO and the U.N. to come investigate," Ziad said.

Fox News' Bret Baier, Mike Emanuel and Ian McCaleb contributed to this report.