State officials are trying to figure out how and why the sensitive information - including children's full names and locations - would remain on hard drives that had been reformatted to eliminate the information before being sent for recycling or disposal.

"We can't confirm or deny it's ours," said Stephanie Marquis, a spokeswoman for the Wisconsin Department of Health and Family Services, on Wednesday. "It's the type of data our agency works with, but it's also data that other agencies work with."

On Monday the Seattle-based Basel Action Network posted on its Web site a copy of a 2001 spreadsheet that listed personal information of 45 children and their guardians in the state program. All names were blacked out.

BAN coordinator Jim Puckett said his group purchased the hard drive for about $20 from a marketplace in Lagos, Nigeria as part of an effort to track the hazardous disposal of computer and electronic refuse overseas.

"There are two reasons we gather hard drives - one, to find out where they're coming from, and two, to show liability beyond environmental liability: the protection of private data," Puckett said.

BAN worked with a Switzerland company to do examinations of the hard drives.

"I call them examinations but there's not really much to it - when people format their hard drives, they erase nothing, just the table of contents. That's easy to recover," Puckett said. "So many of these hard drives still had data that was very alive, just waiting to be grabbed."

Marquis said her department takes the apparent breach very seriously because it goes to great lengths to safeguard private information, but she can't be sure yet that the confidential data came from her agency.

She said the part number of the hard drive doesn't match the part number of any internal equipment her department ever had. Also, the drive has Microsoft Outlook downloaded on it even though the agency hasn't adopted Outlook.

One file on the hard drive that linked the hardware to the department was the resume of an intern who was later hired by the agency but left in 2004. Department officials say that person's resume was only on a personal computer that the person still has.

"Until we get more information, it's difficult to ascertain how this information made it out there," Marquis said. "Is it someone's personal file? Did they take work home? We're not sure yet."

She said her agency's policy in 2001 was to wipe out and reformat hard drives before disposal, and after a more stringent policy was implemented in 2003, data is now not only erased but replaced with all zero values. If there are any problems, she added, the agency simply destroys the hard drive.

The agency hopes to get the hard drive back from BAN to assist its internal investigation.

Puckett said his organization would have no problem returning it as long as the agency isn't trying to cover anything up.

BAN says China and other southeastern Asian nations used to be the main destination for discarded electronics, but Nigeria is becoming a new dumping ground because Nigerians who are especially anxious to bridge the digital divide want used computer parts.

Puckett said it's not a coincidence that a popular e-mail scam in which an individual claims to be exporting a large amount of cash is generally identified as a Nigerian.

"I don't want to pick on Nigerians, but there are people there who are ingenious about scamming money," Puckett said. "If they have access to personal information, they can make their e-mail scams so much more specific, so much more believable."

Computer experts recommend that users dispose of a hard drive by first running commercial software that repeatedly overwrites information with ones and zeros. Alternatively, a person could physically destroy the hard drive or keep it and dispose of the rest of the computer.