This article was reported by Eric Schmitt, Ginger Thompson, Margot Williams and James Glanz, and was written by Mr. Schmitt and Ms. Thompson.

WASHINGTON, Nov. 10 - As the insurgency in Iraq escalated in the spring of 2004, American officials entrusted an Iraqi businessman with issuing weapons to Iraqi police cadets training to help quell the violence.

By all accounts, the businessman, Kassim al-Saffar, a veteran of the Iran-Iraq war, did well at distributing the Pentagon-supplied weapons from the Baghdad Police Academy armory he managed for a military contractor. But, co-workers say, he also turned the armory into his own private arms bazaar with the seemingapproval of some American officials and executives, selling AK-47 assault rifles, Glock pistols and heavy machine guns to anyone with cash in hand - Iraqi militias, South African security guards and even American contractors.

"This was the craziest thing in the world," said John Tisdale, a retired Air Force master sergeant who managed an adjacentwarehouse. "They were taking weapons away by the truckload."

Activities at that armory and other warehouses help explain how the American military lost track of some 190,000 pistols and automatic rifles supplied by the United States to Iraq's security forces in 2004 and 2005, as auditors discovered in the past year.

These discoveries prompted criminal inquiries by the Pentagon and the Justice Department, and stoked fears that the arms could fall into enemy hands and be used against American troops. So far, no missing weapons have been linked to any American deaths, but investigators say that in a country awash with weapons, it may be impossible to trace where some ended up.

While the Pentagon has yet to offer its own accounting of how the weapons channel broke down, it is clear from interviews with two dozen military and civilian investigators, contracting officers, warehouse managers and others that military expediency sometimes ran amok, the lines between legal and illegal were blurred and billions of dollars in arms were handed over to shoestring commands without significant oversight.

In the armory that Mr. Saffar presided over, for example, his dealings were murky. Mr. Tisdale, who recalled seeing a briefcase stuffed with stacks of $20 bills under Mr. Saffar's desk, said he thought Mr. Saffar enriched himself selling American stocks along with guns he acquired from the streets. Mr. Tisdale was supposed to sign off on any transactions by Mr. Saffar, but he said many shipments left the armory without his approval and without the required records.

Ted Nordgaarden, an Alaska state trooper who worked as the police academy's supply chief, said most of the weapons he saw leaving the armory went with a military escort. For his part, Mr. Saffar denies any wrongdoing, including any arms dealings. Nearly a half-dozen American and Iraqi workers say his gun business was an open secret at the armory.

Elsewhere, American officers short-circuited the chain of custody by rushing to Baghdad's airport to claim crates of newly arrived weapons without filing the necessary paperwork. And Iraqis regularly sold or stole the American-supplied weapons, American officers and contractors said.

A shipment of 3,000 Glocks issued to police cadets disappeared within a week when they were sold on the black market, said an American official involved in distributing weapons. Other military sources said the weapons would fetch between five and seven times more than the $200 a police cadet would earn in a month. American military commanders say Iraqi security guards are suspected of stealing hundreds of weapons last year in about 10 major thefts at arms depots at Taji and Abu Ghraib.

The investigations into missing weapons are among the most serious in the widening federal inquiries into billions of dollars in military contracts for the purchase and delivery of weapons, supplies and other matériel to Iraqi and American forces.

Already there is evidence that some American-supplied weapons fell into the hands of guerrillas responsible for attacks against Turkey, an important United States ally. Some investigators said that because military suppliers to the war zone were not required to record serial numbers, it was unlikely that the authorities would ever be able to tell where the weapons went.

Many of those weapons were issued when Gen. David H. Petraeus, now the top American commander in Iraq, was responsible for training and equipping Iraqi security forces in 2004 and 2005. General Petraeus has said that he opted to arm the Iraqi forces as quickly as possible, before tracking systems were fully in place. The Pentagon says it has since tightened its record keeping for the weapons, but government auditors said in interviews that they were not yet convinced that an effective system was in place.

"The problem goes well beyond bookkeeping," said Joseph A. Christoff, the director of international affairs and trade for the Government Accountability Office. Another G.A.O. official said, "There were inquiries from soldiers finding enemy weapons caches, finding AK-47s, and they would ask, 'Did we give these to them?'"

Some military officials involved in supplying the Iraqis describe the sense of urgency they felt and the need to cut through what they saw as a cumbersome military bureaucracy.

A few miles from Mr. Saffar's armory, Maj. John Isgrigg III and Maj. Timmy W. Cox were assigned to issue weapons to the Iraqi military and national guard from early 2004 to 2005. As soon as they heard that a new shipment was arriving, the officers said, they put together a convoy to be the first to claim it, barreling onto the tarmac at Baghdad International Airport and loading the crates of Glocks and AK-47s.

In several telephone interviews and e-mail exchanges, Majors Cox and Isgrigg described a race between themselves and the system. They acknowledged that they did not do everything by the book. They did not always call ahead to the airport to say they were coming. They signed receipts but did not always wait around to fill out inspection reports, known as DD-250s. And they told only certain superior officers about their plans for where the weapons would be delivered.

Major Isgrigg, 46, described the chain of custody as a maze of red tape. Once weapons went into it, it took days for them to be released, he said. Sometimes, he said, a competing unit distributing weapons to the Iraqi police would get to a shipment first, so he and Major Cox would have to wait for the next one. He said that warehouse crews had been infiltrated by Iraqis sympathetic to insurgents, and that sometimes weapons would disappear.

"We had folks getting killed because equipment wasn't moving," said Col. Randy Hinton, the majors' superior officer. "Were there times when all the right forms were not signed? Probably. But we had a mission to do, and we were going to do it the best way we could at that time."

In a phone interview from Bangkok, John Hess, who worked as the assistant director of operations for an American-owned company that helped manage supplies for Iraq, said payments to the companies that supplied arms to Iraq were often delayed because of missing DD-250s. He said he believed that the officers had the right motives but used dangerous methods.

"Once those weapons left normal channels," Mr. Hess said, "none of us were ever sure where they were really going."

Several co-workers complained about the unorthodox tactics of the two officers, including an accusation that Major Cox, 38, was stealing weapons, Major Isgrigg said. However, federal officials said the officers were not the targets of an investigation.

Even when they managed to get weapons to the Iraqi military, Major Isgrigg said, it was hard for him and Major Cox to feel triumphant. The Iraqi commanders could barely keep track of their troops, much less stocks of new weapons, he said. He estimated that 30 percent of the equipment he and Major Cox delivered went to Iraqi soldiers who showed up for duty one day, and disappeared the next.

"There were times we would issue a batch of weapons and within 10 days they would show up at the Enemy Weapons Purchase Program," Major Cox, who is on his second tour in Baghdad, wrote by e-mail, referring to a military effort to buy guns from the streets.

"We didn't always think we were going about things the right way," said Major Isgrigg, who left Iraq in July. But he said he believed that his actions were necessary, saying of his commanders: "They rushed it. Their goal was to get those units standing as fast as possible, and then to get out of there. There was no planning for the long term."

As the American military hurried to train and equip Iraqi security forces in the spring of 2004, the Pentagon turned to contractors to operate warehouses to store equipment and weapons.

Mr. Saffar managed an armory on the grounds of the Baghdad Police Academy, which along with a nearby warehouse was operated by an American-owned company based in Kuwait.

In July, the company, American Logistics Services, which later became Lee Dynamics International, was suspended by the Army from doing future business with the government amid accusations that the company paid hundreds of thousands of dollars in bribes to military contracting officers. The company had won $11 million in contracts to manage five warehouses with arms and other equipment in Iraq.

The company's armory, a long concrete building divided into two sections in the back, was a logistics hub for the new Iraqi police. Crates of AK-47s and Glock pistols purchased by the Pentagon were trucked to the armory by armed convoys from a large warehouse at Abu Ghraib, and Mr. Saffar issued them to cadets.

It was also from this 1,800-square-foot building and six adjacent 40-foot-long metal shipping containers that Mr. Saffar plied his personal arms trade, co-workers said. He sold guns from the black market and from captured stocks. "There wasn't anybody there who didn't know what he was doing," said Mr. Nordgaarden, the Alaska state trooper.

Mr. Tisdale said Mr. Saffar had a steady stream of customers, from Iraqis to South African private security contractors. "There were truckloads of stuff moving out of that armory without my authorization," Mr. Tisdale said.

Mr. Tisdale said that he complained repeatedly to two top American Logistics executives, but they assured him that Mr. Saffar's dealings were proper. The company has not responded to requests for comment.

Mr. Tisdale and other co-workers said they believed that an American military official, Lt. Col. Levonda Joey Selph, an Army officer who oversaw the warehouse contract and whose activities have been part of the investigation into American Logistics, also must have known about the arms dealings. Mr. Tisdale said the colonelregularly visited the armory and met with Mr. Saffar. Mr. Nordgaarden recalled seeing Colonel Selph at the warehouse 8 to 10 times over a year.

In an brief encounter outside her Northern Virginia home, Colonel Selph would say only that she was not guilty of any wrongdoing, and that she was under orders not to speak to the press. She would not say whose orders.

Mr. Saffar, who said he left Iraq in August 2005 when his contract to manage the armory ended, denied that he had run a private arms business. "My work was to issue weapons and ammunition to the Iraqi police," he said in an e-mail message from Bahrain.

Mr. Hess, who was the assistant director of operations for American Logistics, defended Colonel Selph as the one person trying to establish order in the chaos that characterized the early months of the reconstruction effort. And he said that though Mr. Saffar's arms business might look bad from a distance, it hardly raised an eyebrow in Baghdad.

"You're talking about a war zone," Mr. Hess said. "In Iraq, weapons are everywhere."