BAGRAM, Afghanistan -- American investigators armed with a "box full" of cash have paid thousands of dollars to buy back stolen computer drives -- many of which contain sensitive military data, shopkeepers outside the main U.S. military base in Afghanistan said yesterday.

But dozens are still on sale, including memory sticks with information ranging from U.S. troop resumes to photos of Air Force One during President Bush's visit last month.

The surfacing of the stolen computer devices has sparked a probe to discover how security could have been breached at the heavily guarded Bagram base, which coordinates the fight against remnants of the deposed Taliban regime and al-Qaida militants.

U.S. military spokesman Lt. Mike Cody said he could not comment because an investigation was ongoing.

Shopkeepers let an Associated Press reporter review about 40 of the drives on a laptop computer yesterday. Most were blank or did not work, but three contained data, including a soldier's military discharge certificate, troop resumes and photographs of Air Force One during Mr. Bush's visit to Afghanistan last month.

One shopkeeper said soldiers went around the market outside the base Thursday carrying "a box full of afghanis [the Afghan currency], buying all they could find."

He said he sold about 50 for $2,000, roughly $40 each. A day earlier, he was selling them for about half that price. "They said they wanted them all, and price wasn't important," the shopkeeper said.

The troops hadn't returned to the market by yesterday afternoon despite dozens of the flash drives still being available. Another shopkeeper, who declined to be identified for the same reason, said the troops promised to return.

Included on some memory drives seen by AP this week were the Social Security numbers of hundreds of soldiers, including four generals, and lists of troops who completed nuclear, chemical and biological warfare training.

The Los Angeles Times also reported that some drives had classified military secrets, including maps, charts and intelligence reports that appeared to detail how Taliban and al-Qaida leaders have been using southwestern Pakistan as a planning and training base for attacks.

The Times also said the drives appeared to contain the identities of Afghan sources spying for U.S. Special Forces that operate out of Bagram.

The shopkeepers have said they were not interested in the data and were only selling the drives for the value of the hardware.

They say the drives were stolen by some of the 2,000 Afghans employed as cleaners, office staff and laborers at Bagram. Though workers 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.