Danish troops in southern Iraq sealed off an area Monday where 36 mortar shells thought to contain a liquid blister agent were found, the army said, as they prepared the weapons for another round of tests by U.S.-led experts.

The Iraqi Survey Group (search), an American-led group of intelligence analysts, interrogators and translators, will investigate the 120mm mortar shells that Danish and Icelandic troops uncovered last week near Qurnah, north of the city of Basra, where Denmark's 410 soldiers are based.

The 14-member group is expected to arrive Tuesday morning, the army said.

Preliminary tests on the plastic-wrapped but damaged shells showed they contained a liquid blister agent.

Initial tests by field troops are designed to favor a positive reading, erring on the side of caution to protect soldiers. More sophisticated tests are often necessary.

The Danish and U.S. military believe the shells could be left over from the eight-year war between Iraq and Iran, which ended in 1988.

Speaking in Baghdad, U.S. Gen. Mark Kimmitt said the rounds did appear to be blister agents.

"The age of those would indicate that those were probably 10 to 20 years old," he said, adding their location near the border with Iran made it likely they were used in that war.

"So I think we'll probably have some results in the next couple of days confirming it," he said.

"We expect they will start making the tests on Tuesday but I cannot say when the results will be made public," Maj. Kim Gruenberger of the Danish Army Operational Command (search) told The Associated Press. "We hope to get results as soon as possible. A good guess is at the end of week," he said.

Danish troops sealed off the area where the shells were found and handed out fliers to residents warning them to stay away if the shells turn out to hold chemicals.

Adnan Khalifa, an Iraqi who lives near the sealed-off area, told a Danish TV2 reporter in Basra that he helped bury the mortar shells three years ago. "We also dumped some of them in the river," he said.

Some Iraqis have said there are several caches of mortar shells in the area, including a stockpile dumped in the Tigris River that could contain as many as 400 shells, army officials in Denmark said.

"When the engineers have been released from their present finding, they will start investigating the areas which Iraqis have pointed at," the Danish Army Operational Command said.

Before the war, the United States asserted Iraq still had stockpiles of mustard gas, a World War I-era blister agent that is stored in liquid form. The chemical burns skin, eyes and lungs.

U.S. intelligence officials also claimed Iraq had sarin (search), cyclosarin (search) and VX (search), which are extremely deadly nerve agents.

In the weeks after the Iraq war, the U.S.-led coalition found several caches that tested positive for mustard gas but later turned out to contain missile fuel or other chemicals.

Other discoveries early in the U.S.-led occupation turned out to be old caches that already had been tagged by United Nations inspectors and were scheduled for destruction.

Saddam Hussein's regime used chemical weapons against Iranian soldiers during the Iran-Iraq war and killed an estimated 5,000 Kurdish civilians in a chemical attack on the northern city of Halabja in 1988.

In October, Dutch marines found several dozen artillery shells dating to the 1991 Gulf War in the southern Iraqi town of Samawah, but the shells contained no biological or chemical agents. Samawah is nearly 100 miles west of the southern region where the Danes discovered shells last week.

In April, U.S. troops found a dozen 55-gallon drums near the northern Iraqi town of Baiji. Preliminary tests found possible evidence of a nerve agent and a blister agent, but later tests found the contents were not chemical weapons.