A shopkeeper outside the U.S.-led coalition headquarters in Afghanistan was selling computer memory drives Wednesday containing seemingly sensitive military data stolen from inside the base — including the Social Security numbers of four American generals.

This shopkeeper was apparently not the only merchant in local bazaars trying to get some cash in exchange for hardware and software containing such files.

The surfacing of the stolen computer devices has sparked an urgent American military probe for the source of the embarrassing security breach, which has led to disks with the personal letters and biographies of soldiers and lists of troops who completed nuclear, chemical and biological warfare training going on sale for $20 to $50.

Five military investigators, surrounded by heavily armed plainclothes U.S. soldiers, searched many of the two dozen rundown shops outside the sprawling base.

Asked if any discs had been found, one soldier, who declined to give his name, said: "We are looking. That's all I can say."

The shopkeeper, who spoke on condition of anonymity because of fears he may be arrested, said he was not interested in the data stored on the memory sticks and was selling them for the value of the hardware.

"They were all stolen from offices inside the base by the Afghans working there," he said. "I get them all the time."

About 2,000 Afghans are employed as cleaners, office staff and laborers at the Bagram base.

News of the breach was first reported by the Los Angeles Times on Monday. The paper said its Though they are searched coming in and out of the base, the flash drives are the size of a finger and can easily be concealed on a body.

The shopkeeper showed an Associated Press reporter a bag of about 15 and allowed them to be reviewed on a laptop computer. Only four contained data. The rest did not work or were blank. reporter saw files containing classified military assessments of enemy targets, names of corrupt Afghan officials and descriptions of American defenses.

U.S. military spokesman Lt. Mike Cody said the military "has ordered an investigation into allegations that sensitive military items are being sold in local bazaars.

"Coalition officials regularly survey bazaars across Afghanistan for the presence of contraband materials, but thus far have not uncovered sensitive or classified items," he said.

U.S. commander Lt. Gen. Karl W. Eikenberry has ordered a review of policies and procedures relating to the accountability of computer hardware and software, Cody said.

The shops around Bagram sprung up when U.S. forces took over the base in 2001 after ousting the Taliban for harboring al-Qaida leader Osama bin Laden.

They sell a range of military equipment, much of which has been stolen from the base, according to several shopkeepers — all of whom declined to give their names for fear of repercussions.

One shopkeeper wanted $20 for a used U.S. soldier's uniform and said he could get more.

Other items apparently were stolen from a duty-free store on the base, including range-finding binoculars and handheld global positioning systems — items that could be useful to Taliban rebels, who have stepped up their insurgency in the past year.

The computer files seen by the AP ranged from the very personal, such as a soldier's letter to the wife of a dead comrade, to confidential personnel information.

Social Security numbers were listed next to the names of hundreds of soldiers, including Maj. Gen. Jason Kamiya, who left Afghanistan in February after serving for a year as the coalition's operational commander.

One document listed the names of 20 members of a platoon who had undergone "the required Nuclear Biological Chemical (NBC) training and chamber exercise." It did not elaborate.

Another listed the names of 16 soldiers and the types of weapons they had been trained on.

There were biographies of six soldiers, including a sergeant who had served in Kosovo, Iraq and Afghanistan.

Two of the drives contained several photographs, one showing a group of about 40 soldiers posing at a base, while others had troops inside a helicopter.

A 502-page manual on how to operate a CH-47 Chinook chopper, a mainstay of the 18,000 U.S. troops serving in Afghanistan, was also there, including photos and diagrams.

Many of the other goods on sale in the stores still had stickers indicating the price at the military store. The Afghan shops were selling them for about 25 percent less.

In one store, two Afghans with long flowing black beards were haggling over the price of compasses.

Nearby, two young boys were trying to sell cartons of fresh yogurt. One, who gave his name as Nazar, said a friend had stolen them from the military mess hall.