By James Glanz

Equipment plundered from dozens of sites in Saddam Hussein's vast complex for manufacturing weapons is beginning to surface in open markets in Iraq's major cities and at border crossings. Looters stormed the sites two years ago when Mr. Hussein's government fell, and the fate of much of the equipment has remained a mystery.

But on a recent day near the Iranian border, resting in great chunks on a weedy lot in front of an Iraqi Border Patrol warehouse, were pieces of machine tools, some weighing as much as a car, that investigators say formed the heart of a factory that made artillery shells near Baghdad. Military equipment, including parts for obscure armaments used by Mr. Hussein's army, is also turning up in Baghdad and Mosul in the north, they say.

For more than a year, large quantities of scrap metal from some of the sites have routinely been filling the scrap yards of Iraq and neighboring countries like Jordan. But with this new emergence of a huge panoply of intact factory, machine and vehicle parts, it appears that some looters may have held back the troves they stole two years ago, waiting for prices to rise.

"Spare parts?" said Staff Sgt. William Larock, an American reservist in a division out of Rochester, N.Y., who is stationed near Munthriya and is coordinating repairs of some of Mr. Hussein's old troop carriers to be used for the new Iraqi Army. "A lot of them come from the market in Baghdad." Sergeant Larock said that some of his repairs to the vehicles, which Mr. Hussein bought from a manufacturer in Brazil, were being delayed because the asking price on the highly specialized wheels - clearly stolen long ago from those same vehicles - was too high. "That's why these things are sitting on blocks," he said with a faint smile.

Interviews with people who identified themselves as arms dealers or members of the resistance in Baghdad, Falluja and other Iraqi cities indicate that a parallel black market operates in the explosives looted from some of the same sites. In fact, sketchy descriptions by members of the Iraqi resistance suggest that the arms market is also a highly developed enterprise with brokers, buyers and looters who have stockpiled their products, including artillery shells, mortar rounds and Kalashnikov rifles. One former Iraqi army officer who said that he had joined the mujahedeen said that in Sadr City, for example, a few trusted brokers would take prospective buyers to weapons caches that ranged in size from a few rounds buried in a garden to whole rooms of ordnance. If the broker and the buyers agreed on a price, the buyers would arrive a day or two later with a vehicle to drive their purchases away. The broker and the stockpilers would have worked out their respective cuts in advance.

Witnesses described looters of varying degrees of sophistication, from local people who stormed the sites in search of precious metals after Mr. Hussein's security forces fled to highly organized operations that arrived with cranes and semitrailer trucks. Some of the most organized groups arrived earliest and drove away with largely intact equipment.

When it comes to buying run-of-the-mill equipment and spare parts that were obviously looted in the past, the American military appears to have adopted some version of a don't-ask, don't-tell policy concerning where the materials originated. The materials, after all, are now being sold openly in street markets. So the Americans appear resigned to buying the equipment back rather than seizing it.

But the pieces of the artillery factory were headed to Iran when they were seized a few months ago by Iraqi border guards. They appeared to have been cut apart just so; the dismemberment allowed the material to meet the official definition of scrap, but did no damage that would prevent the pieces from being reassembled. "They cut in places that were not important," said Brig. Gen. Nazim Shariff Muhammad, leader of the Iraqi Border Guard in Diyala Province, standing with his right foot perched on part of the machinery. "So they let us think it was going to be used as scrap metal."

Much more valuable machinery also vanished from some of the sites in the weeks after the invasion: so-called dual-use equipment, which could be used in civilian manufacturing and in building parts for nuclear weapons. Witness accounts have indicated that much of it was carried off in systematic looting in the six to eight weeks after Baghdad fell on April 9, 2003. That equipment, which investigators say was more likely coveted for its monetary value rather than its military value, disappeared without any public trace. If an entire artillery factory could come this close to crossing the border, some military specialists say, then the dual-use equipment had a chance of getting out as well.

From Baghdad's main roads, Munthriya is the nearest border crossing, making it a natural way station for anything transported, legitimately or not, from the area around the capital. That part of the Iraqi frontier, about 90 miles northeast of Baghdad and just south of Kurdistan, is a place out of time. For reasons that seem to be lost in the mists of history, many of the border outposts of Iraq and Iran look like miniature castles, complete with crenelated walls and cylindrical watchtowers at the corners. The outposts face each other across a no man's land of grassy hills that are still heavily mined, a legacy of the Iran-Iraq war. In the hazy distance, the Iranian mountains rise. "They are watching us," said Warrant Officer Aso Ahmed Showkat at the border post called Yassin Castle, pointing to one of the Iranian outposts.

In the weeks after Baghdad fell, the roads in that part of Iraq were choked with trucks carrying scrap metal, looted generators, cars, chopped-up tanks and other equipment, many witnesses said. Mukhtar Ahmed, who owns a tea shop in Bashmakh, north of Munthriya, estimated that as many as 300 trucks a day passed his shop at the height of the activity. Lt. Col. Ali Muhammad Darweesh Al Kakay, who came south in that period with a Kurdish pesh merga force and is now a border official, said, "Everything, you can smuggle at that time."

Since the border patrol began mobilizing in June 2003, General Nazim said, the border had been secure, and only scrap dealers with government permits had been allowed to transport materials into Iran through the Munthriya crossing. Specific rules for what constituted scrap had been set up. A tank, for example, had to be cut into at least eight pieces, or it was judged that someone could put it back together.

In General Nazim's view, the episode of the artillery factory is a case in point. His border guards told him that there were eight or nine large trucks filled with odd-looking scrap. "But the materials inside the trucks were not scrap," he said. "I knew this was something very strange." Engineers identified the equipment as a set of huge machine tools for making shells, and pinpointed where it had all come from: a military site called Al Walid, near Baghdad.

Now somewhat rusted from exposure, the material sits in front of the border police headquarters, and in a fitting twist, some of its more precious components have been looted a second time. John Pike, director of GlobalSecurity.org, said the story of the artillery factory was not necessarily reassuring. "This is just the stuff that got caught," Mr. Pike said when a reporter contacted him from Forward Operating Base Cobra, an American Army base near the border. "The more interesting stuff would have gone out first," he said.